Should You Use Natural Seawater In Your Aquarium

It seems very reasonable doesn’t it. We keep seawater aquariums and so why not put [tag-tec]natural seawater[/tag-tec] in them. It saves money too, no more buying those expensive buckets of dry salt mix.

The first consideration is availability. Seawater is heavy, around 10lbs per gallon. If the aquarium is fairly large the amount required will be many gallons, much more if it is an initial fill. Lots of large containers, all suitably safe for seawater, plus a vehicle that can safely transport the bulk and weight. Most aquarists live away from the sea, and the dry salt mix is the obvious way to go.
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  1. What a joke. You were completely biased from the start. Clearly you are against NSW so why write the article? 1,000 litre container, a generator and a bilge pump and I can collect a tonne of seawater at a time without any issues. That will last me several months. The initial cost to buy the above is negligible compared to artificial salt + RODI fresh.

  2. No, Jim! I’m not against NSW. After all, this is what Mother Nature provides. It follows, therefore, that it should be ok for captive reefs.
    I wrote the text from the perspective of the majority of aquarists. They have to get to the sea, collect, and transport. Unfortunately, there is the real question of pollution for many.
    Clearly you have the access, the seawater quality, the equipment and transportation availability for collection. 1000 litres is a lot of seawater, and a lot of weight. How many can collect/transport that?
    I tried to look at the potential practical problems that would be faced. Seawater that is clean, can be collected and stored safely is an option to a few – and in the past some public aquariums did this, but some now use salt (no doubt at a considerable discount).

  3. Well, I am not very near to the sea, but I took the efforts to try natural sea water!
    I have my main tank with synthetic salt water which is doing great, but some thing was lacking out there.
    To experiment I set up a small tank and used natural sea water, it was just filtered for large particles and then dumped it the new clean tank, with no sand, no skimmer, etc.
    It had only a basic power head for circulation.
    It was a total success. I put some of my existing corals in it, and they were never as the were in my main tank, they sensitive types appeared to be hardy……………
    The results were great color, more than full polyp extension, fast growth, etc.
    This was observed for a year, and the temp tank has out grown its capacity of coral housing without any new addition!
    The natural sea water was replaced every three weeks.
    I think, synthetic salts formulas lack something untraceable, which makes the difference………….
    The natural seawater is as wonder, wish it could flow in my taps!

  4. Hi Sam.
    Now that’s very interesting! I wonder how many have done what you did, and run NSW against synthetic. Often that’s how we advance, with trial and error on this and that.
    There is no doubt that Mother Nature’s product is best, provided it hasn’t been tainted by humankind. One ‘synthetic’ salt manufacturer obtains salt from the Red Sea, by evaporating the liquid. Probably not quite as straightforward as that!
    However, the fact remains that most aquarists don’t have the storage and transportation (and/or the will?) to go to the sea or ocean.
    I wonder what made your corals happier? Perhaps the synthetic mixes are too chemically ‘harsh’? Must say though that in my soft coral tank my main problem is overgrowth.
    Great to read of experiments such as this. Though anecdotal, they cause questions, which can only be good.

  5. I had always heard one side of this debate – that natural sea water is plagued with parasites and pollution – until I visited my now-local fish shop. This guy has the most beautiful coral collections I have ever seen. Vibrant SPS like nothing I had seen in pictures, healthy fish, all around great success. I couldn’t believe it. I’m in the process of converting my fish-only setup now! Can’t wait to try it with corals

  6. Believe or not, i live in Mauritius, a tropical island in the indian ocean for those who don’t know and I have owned an aquarium all my life. The funny thing is that I have always spent huge sum of money buying all kinds of plants, imported fishes, etc for fresh water fishes until fairly recently, i asked myself why not try sea water fishes.

    So, sea water is readily available and I have a wide variety of fishes that I can fish myself by the seaside, not mentioning that all that is free of cost. Sea water fishes are wild, i have no idea which is the predator or which one only feeds on seaweeds but I am learning fast from watching it live in my aquarium!! My small blue fishes kept disappearing one at a time when I finally spot the my red fish with huge eyes taking it all at one go! Apparently all red fishes are predators, and the huge eye was night hunting… I should have realised. Anyways, my concern is that, i don’t know how to keep my aquarium filled with fresh sea water clean. It turns cloudy, slightly brownish after a week or so. I wonder whether it is my sea weeds which I think must be missing sunlight or the coral itself… Anyways, all this is new for me, i may have grown into an expert in fresh water fishes but still a novice in sea water fishes. Till now, I am simply exchanging 10L of water every other day to keep my aquarium clear.

  7. It would have been nice if this article could have explained more about actually using NSW vs RO Unit + Salt rather than just “you have to lug it around”, im sure people already know that.

    Sure mention that 1litre weighs around 1.024kg… but more would be nice.

    I’m not exactly an expert (never tried it – hence why I am looking) but it seems obvious not to trust the quality near shore, so might be worth testing the water before you take some? And not to assume it will always be the same as surface run off and near river deltas can change it depending on the type of rain (acid rain and all them worries). Just like the people who collect rain water for their aquariums, we can’t rely on it being the same from one day to another.

    Any other info would be brilliant.

    One thing I wondered – if you lived on the door step of the sea, assuming it was away from pollutant sites, could you constantly pump water (slowly, and assuming temperature matches fine) through your aquarium and have no need for any kind of filtration/skimming/etc? Sounds like a dream! 😉

  8. I’m not against natural seawater at all. My attitude is that Mother Nature is in charge and knows best.

    I live by the sea (cold) but use synthetic. The reason for this is that I cannot trust the quality of the natural seawater (NSW). If I could by going offshore I don’t have the transportation facility, even if I were to collect a small amount at a time.

    As I don’t use NSW I can’t really give opinions as to how it should be used. However, I do know of aquarists who use nothing else but NSW. They say that their method is the same as it would be for synthetic, that is they do the necessary routine seawater changes and also add any required supplement, for example calcium. Some find it strange that a supplement should be used with the natural stuff, but the same happens in the aquarium if there is a demand – it gets used up.

    The idea of slow-pumping NSW through an aquarium isn’t new though no doubt it is hardly used in our hobbyist world. The public aquarium fairly close to me uses this method on their main tanks, though they have smaller tanks that are dealt with in the normal way. The seawater is collected well offshore then pumped through numerous filters which deal with large, small and miniscule debris and also hopefully remove any living nasties. The aquariums do seem to be doing well overall though there are losses from time to time. As a commercial enterprise cost will be high on the agenda so the power and filtration requirements will have been balanced against the cost of sysnthitic salt.

    To say again – if an aquarist is able to obtain clean natural seawater in sufficient quantity, in other words has the collection and transportation facilities then there isn’t any reason why natural seawater shouldn’t be used. However, I stand by the suggestion that synthetic seawater is the way to go for most marine aquarists on the basis that they aren’t by the sea, or haven’t the collection and/or transportation facilities.
    .-= John´s last blog ..Aggression On The Reef =-.

  9. This is such a great debate. I have always used synthetic salt mix. I was living in Virginia and NSW was not available to me. I have always wondered if NSW would be okay to use. Since then I have moved Florida. I now live by the beach. I was setting up my 125 gallon tank. It was a hard decision to go natural or continue using synthetic. Despite all the oppositions I had to try the NSW. I agree with John on one point! Obtaining the NSW is no easy feat! I had 2 pickup trucks, a trailer, 4 grown men, 30 – 5 gallon buckets. I found the most isolated spot away from fresh water run offs. Had to find the closest spot from beach to road. Once all of this was accomplished, It was then that the manual labor began. It took just around an hour with all of us working very hard. Once the water was loaded. Then the trip back home which wasnt that bad. 40 miles or so. Once I had them at the carport, 30 buckets being carried up a flight of stairs. I used a very fine neat to trap large particles and floating algae. Once the tank was full. I turned on 2 aqua clear 110’s , 1 eheim 2215, 2 power heads, 1 uv sterilizer and protein skimmer. You can immediately see the skimmer taking action with dirty crude from the water. for 5 hours it was producing this dirt. Now its seems prett clean after 24 hours. The water is very clean. A tad bit cloudy yet but this even happens with synthetic mixtures. Okay My parameters are as follows: Ammonia 0, Nitrites 0, Nitrates 0, PH 8.4, phosphates 0. So far so good. I will continue to monitor the paramaters for several days. I do agree with others on here, What better to keep your fish than something natural. This is where they come from. Unless you have some industrial waste runoff or fresh water runoff, I dont see what the problem would be. Also some companies sell NSW for $15.00 to $20.00 dollars for 2 gallon jugs. You do the math on that one. So lets see what happens but I have good feelings about this. I will post soon and let you guys know about my findings on my test!

  10. Thanks very much for that Ray, very interesting. The ‘Sunshine State’ eh, lucky you!

    As time goes on it will be good to know what happens.

    Much has been said about how well organisms do in NSW. The only things that I can think of that possibly could be the reason are that the manufacturer’s oft made claim of ‘indistinguishable from Nature’s own’ is perhaps a bit over ambitious, and that synthetic seawater is ‘harsh’ chemically, as opposed to mature superbly mixed NSW.

  11. Hello Everyone!

    Im back to post some information on my findings. Its been 13 days since I set up my tank with NSW. I previously posted my parameters upon set up 2 weeks ago. on the second day of setup I noticed the tank was going through its diatom bloom. It promoted all the light brown film on the substrate. It is almost completely gone. Just a few little spots I see here and there. They are approximately dime to quarter size in diameter but very faint and hard to see. The water is crystal clear. I added fish also. 8 green chromis and 1 six line wrasse. G/F really wanted the six line wrasse. I was hestitant but gave in. I thought it would probably be okay but didnt want the little guy to persish if anything went wrong with the water parameters. So far so good. I have not noticed any stress on any of the fish. No irratical swimming or heaving breathing from any of the inhabitants. The proptein skimmer is still skimming a nice chunk of stuff but at a lower lolume than previously noted. The UV sterilizer has not been turned off since the start of the tank. I want to make sure that any bacteria gets treated with germicidal bulb. In 2 weeks im planning on turning it off once I add Live lock to help promote corraline algae. The water has been evaporating at a higher rate than im used to up north. Maybe its me but I have had to replace approximately 10 gallons of RO/DI water into the tank. I just top off the tank with the clean water NO SALT of coarse. This would be defeating my purpose of experimenting with NSW is I added a grain of synthetic. So, I took even more test today. Here is what my parameters are as of today:
    Ammonia: 0
    Nitrate: 0
    Nitrite: 0
    PH: 7.8 ( the PH is a tad low will be adding additive to increase)
    Calcium: 420 PPM ( I have not added anything to get this) perfect
    Magnesium: 1,250 (I have not added anything to get this) perfect
    dKH: 12 or 196.9 ( I have not added anything to get this) Perfect.

    As you can all see. It seems so far that using NSW from a good source can be extremely beneficial. I have all good parameters except for the PH which is any easy fix. Other than that its great. I have had a serious problem in the past keeping my calcium and some other elements in tact. Now seems if everything goes well. All I have to do is keep these parameters at these levels. John, I am starting to believe in your theory. I am thinking that what you mentioned previously is true about some trace element that is undetectable. I will continue to use NSW as long as the water is collected from a good source. Do your research, scout the areas before just jumping in any saltwater source. I used Google earth to be able to see if there were any fresh water runoffs on the area. I will let you guys know more about what happens in the next few weeks! Later everyone, Happy Reef and Saltwater Fish Keeping!

  12. Once again Ray….thank you so much for that, there’s not a great deal written for ordinary aquarists about NSW/artificial mixes.

    Your parameters are good (you’re dealing with pH). The diatoms will have disappeared when the silicon ran out, it’s pretty certain they won’t return, at least at the original density.

    With routine seawater changes to ‘freshen’ up the aquarium environment should remain good.

    You’re adding to the minority of marine aquarists who use NSW and who report great results.

    If I may mention….I agree totally that artificial salt must not be added in a procedure/test such as yours. However, watch for any SG drop caused by ‘salt creep’, though it could seem very minor it can have an effect over a period of time.

  13. This new idea of having saltwater in our own aquariums is quite new and controversial. This is the type of topic that needs to be researched and studied to assure that species immersed in this kind of environment will be safe and healthy. If not, tropical freshwater aquarium can be an another option.

  14. Hi Jean.

    Saltwater aquariums aren’t exactly a new idea, they’ve been around for decades. They have now reached an advanced state – just have a look at some of the reef aquariums that can be seen on the internet. The ability of aquarists to maintain healthy marine aquariums has been proved beyond doubt, but there remains the need for newcomers to research and learn of course, and there will always be those that are more advanced and move the hobby forward.

  15. hello ray..

    are you still on here mate? iam from the east coast of england
    ( uk ) ive just started up a marine tank.( 7weeks ago) was going to mix my own salt water when i decided to collect (N.S.W.) iam only 5mins from the beach!! they say that the north sea is dirty, well my tank is do great.!!

    i have an 800lt tank with a sump on the botton, with a protein skimmer, 6500, ocean runner pump, and a seio, m2600 power head.

    when i filled the tank up i put in about 100kg of live rock, and lelf the power head running for two weeks, after two weeks i done a test, ammonia= 0.ppm
    p.h= 8.2
    nitrite = 0.ppm
    nitrate= 0.ppm

    done a test on week 3 the p.h= 8.4 ammonia =0.ppm, nitrite= 0.ppm, nitrate= 0.ppm. ( i think its down to N.S.W.)

    on the 6/2/2011 i put in a sailfin tang with 2 cleaner shrimp.

    on the 13/2/2011 i put in two clown fish, i all so have a couple of star fish , and an hermit crab that have come of the live rock.

    everythink is do well, my water tests are still giveing the same reading, my salinity reading is (35ppt ) which is great. ive just done my first wate change with (N.S.W.) everythink is still great !!

    cheers Terry.

  16. You’ve achieved what many who have used natural sea water (NSW) have reported – got great results! Goes to show that Mother Nature does it better. Sadly for most of us (including me) NSW is not practical to collect.
    As I’ve said before, the only thing that I can guess at as being the main difference is that Mother Nature’s mix is very mature and contains all – maybe there’s something in the seawater that analysts have not detected, though I doubt it.

  17. Hey Terry im still here. I wish i could post a picture or video of my feef tank! Its looking really good! I have even added a t.crocea clam that is doing fantastic. I am setting up another tank, i will be using nsw once again. The same routine as before. Gather nsw, filter the water with a fine net or mesh into the aquarium to collect debris. Turn on filters and uv sterilizer. MOST IMPORTANTLY, allow your tank to mature! No matter what anyone says! Using nsw doesnt give you a magical pass on cycling! It will be faster than mixes but you still nwwd for you tank to mature and develop that beneficial bacteria. Many may ask, so why use nsw if i still need ro cycle? First it will cycle faster! Second, i truly believe that there is an element that is in nsw that is lacking in synthetic. All of your fish, coral, inverts etc will thrive in the natural sea water! Terry please make sure that your water is cleaned in a calculated process through filtration and uv sterilization. Give it some time. Check your parameters frequently, not just the common thing but magnesium, calcium, iodine and such! You will notice that nsw will have all elements needed from the beginning! All you need rondo is maintain it! Hope this helps! Havent been on lately, been busy with work lol! Happy reef keeping everyone!

  18. I’ve got a 50gal that i use NSW and sand and live rock and corals and fish all collected from the same reef. Its has been working fine now for almost a year and the best part is that its all free. I can park pretty close to the water at a beach where i can look a mile in both directions and so nobody. I usually collect my aquarium stuff when i go spear fishing and get a pretty good work out from it. I prefer to catch my aquarium fish at night when i can walk through tidal pools and swim through the reef with a couple nets and a dive light(pelican) which i blind them with before abducting them. I also prefer the to be alone in the water at night time in the reef because you cant see behind you and you have no idea what is in the water with you and it adds an element of danger to a 2:00am adventure.

  19. Hi Peter.
    Now that’s something different! It must be great to be near a wild reef and be able to collect everything you need. You’ll be able to measure the exact seawater parameters if desired. The swimming on the reef whenever wanted must be wonderful though I’m not sure about the 2.00am bit. I’ve been fortunate to visit a lot of reefs in various parts of the world but live nowhere near one, the climate is warm to cold here.

  20. Great article- loved everyone’s opinion…I also live in Florida on the water and am lucky to have a boat in the backyard and it takes me 10 min to get to “deep blue” water. I have a 80 gallon clean plastic container that I use to collect the water but my questions is this: what is the best and fastest way to to plumb it from there to the tank (about 50-60 yards)? I have been using just an old RIo pump and some garden hose but I figure someone out there has got a better way with a ball valve to turn it on and off as needed at the aquarium. Thanks in advance for any answers.

  21. Hey bruce,

    Sounds great having that access! We are fortunate wencan do this. I am assuming you want to put your resevoir of nsw connected to you aquarium display right? I think thats a great idea the problem would be the following: 1st the water wuld not be xlean entering your tank. The water should be cleaned by skimming, uv sterilization and filtration. 2nd, you can connect it in varies ways but remember, your tank water will evaporate, salt does not! So you will steadily increase your salinity/sg to a staggering elevation threw time! I would recommend a ro/do system with clean automatic top off! Take your 80 gallon container and store your nsw. You can add a filtration system and uv sterilzer with power heads in it. Use it for you water changes instead! This will give you time to clean that water out completely and also have an unlimited amount of new fresh saltwater for your water changes! Hopes this helps bruce.

  22. There is no specific way we have to follow, i agree John fully, and agree others too since i live in the Maldives and been in this hobby for 12 years on and off. I always used NSW since there is no way i can purchase synthetic salt from my country. I have tried different ways, had water straight after collecting. It takes 5 mins to bring, and its clear unpolluted water most of the time. Also i do water changes by storing NSW by collecting and storing in plastic containers in the hope of killing off any nutrients that might be in it. Important thing is i have to level temperature and add freshwater to get the correct salinity levels.

    So from my experience, if i had the option to buy salt mix, i would use it for sure, WHY? coz i can never achieve the same quality, same condition, same levels in NSW ever ytime i do a water change, sometimes the water i collect have many nutrients and i have algae blooms, other times some other matter. And anyone who keeps sensitive corals knows that a change in water parameters does do a lot of harm to the corals, it might not show in show in short term, but in long term it affects the corals badly.

    So my bottom line is, NSW is great if you can afford to have it, free even though a lot of effort. At the same time salt mixes are great in the sense that i can know i can achieve the same parameters every time i do a water change. And for those who have differences in noticing coral growth and health of it, we cannot prove its because of NSW coz 99% of all famous and great reefkeepers use salt mix, so we cannot argue that.

    So all i have to say is we can never say NSW is bad coz its mother nature, but due to the factors i’ve mentioned above, its not always the best choice for your corals due to the influence of other factors of mother nature. My corals might be doing great in NSW bcoz they are wild, not cultured. and if i had cultured corals in NSW it might affect badly too, i would love to hear comments from experts.

  23. Hello Xlman.
    Thanks for your input. It’s very interesting particularly as it comes from someone with a coral reef on their doorstep and an available NSW supply. I have to say that if I had uncontaminated NSW available I would definitely try it. The usual problems with NSW are first the major one – getting it (transport etc), then ensuring it is generally clean including pollution and, as you say, maintaining parameters (though the same problem with parameters can arise with manufactured salt).
    I had the good fortune to visit the Maldives (the island was Kanifinolu, I’ve probably mispelt it, sorry) and it was great snorkelling over the reef and just relaxing in general.

  24. Hi. Can anyone tell me.Can I top up my Synthetic salt water Aquarium with NSW water?Your help will be appreciated.
    Thanks Koos.

  25. Hello Koos.
    Yes you can. Make sure the NSW (natural seawater) is safe, that is not polluted, and at the same salinity as your aquarium seawater. If you’ve been using a synthetic mix then it could be easier to slowly alter the synthetic mix in the aquarium to match the NSW (there are some who have reduced the salinity of the NSW if needed by carefully adding RO (reverse osmosis) water but this is creating work for the future that isn’t necessary). To find out the NSW salinity it needs to be heated to the aquarium temperature first before the salinity is measured as temperature has an effect.
    If you are adding a very small amount of NSW (compared to the total aquarium seawater gallonage) then matching the seawater salinity isn’t absolutely necessary though it should still be heated. The overall salinity will match over time. Changes should always be gradual.

  26. I have used sea water on my last 2 tanks. The tank was set up on synthetic and i vary the water change between natural sea water and salt. the reason for this is im still not brave enough to just use nsw 🙂 i collect it from near the shore when the tide is coming in, i may have option in summer of collecting from deep.
    Through this winter it was proving difficult to collect so i went back onto synthetic and i would have to say that my tank isnt doing half as well!!!

  27. Hello Dave.
    Like so many others you report how well your system does with NSW. As you realise the greatest danger is pollution. Why systems do so well with NSW I cannot state categorically – but it seems to me Mother Nature’s own is very mature and directly suitable, whereas synthetic mixes are more harsh even after mixing for 24 hours or so. Or maybe there’s an ingredient in NSW that’s not fully recognised for its importance, but I doubt that!

  28. Hello everyone! its been a while since ive been on here. Wanted to let everyone know that my tank is doing great. I stopped using NSW for a while and noticed a decline in my corals, Corraline algae and such. Started adding trace elements and dosing calcium but the tank is not doing as well as it was when i was using NSW. So this weekend its back to the beach. Seems that its harder for my tank to deplete all the elements found in nature rather than usuing man made stuff. Just thought Id share this with my fellow aquarist. Wish we could post pics on here to show you what I am meaning by all this. Frankly even the coloration of my fish have declined. They were much brighter before than they are now. For anyone intending to us this method of harvesting NSW “DO NOT PUT IT STRAIGHT INTO YOUR TANK”! I cannot express this enough! Get a 55 Gallon Drum or Trash can, Place the water in there for at least 48 hours with a filter, Power head and if possible a UV sterilizer. Then use as water change water. You will be very happy eith results! Happy reefing everyone! send me a message from time to time I feel so not loved by you all! LOL my email is [email protected] from Destin , Florida! talk to you guys later!

  29. Nice to hear again Ray. Agree with what you say about NSW being ‘treated’ before it goes in the display aquarium. Despite the fact (I think I can call it fact?) that the natural stuff is best caution remains the rule.

  30. Hey John im experimenting once again. This time to examine how fast corraline algae responds to the NSW. For some reason its moderate growing with mixes. So we spent all day today changes things around. We also changes filtration system with higher out flows to seed the corraline algae better! Will take a few pic before and after and email to whoever wants to see results if its any different.

  31. Hello. In my reef system I use an artificial salt mix as it isn’t practical to use NSW. The corraline grows steadily and makes some very interesting shapes. I need to clean it off the glass, particularly in the corners once every three months generally, so it’s slow growing (which from a cleaning point of view is an advantage). The lighting is low power, a bank of five fluorescents, blue and marine white.
    I suppose theoretically there should not be a great deal of difference between growth with NSW or artificial provided the mixtures are up to spec and kept so.
    It will be interesting to see what happens.

  32. Hi all, I am just in the process of starting my first reerf tank, looking forward to it very much, have now spent months researching everything (I hope) I live on the Isle of Man (surrounded by sea) which is why I think I shall try the NSW route, after filling aquarium and running filter, protein skimmer, I’m also adding in a calcium reactor etc for 3 weeks, say all my readings are fine, and my tank etc in the future is great, how do I get my top up water to the same levels as my display tank.
    As I can only see this being stored in a large vessel with a filter & heater, or will I require another protein skimmer on this vessel as well???
    Everyone in discussing NSW, has anyone tried natural sand as a live sand???
    Cheers everyone

  33. Hello Phil. Natural seawater (NSW) does seem to be getting some accolades which isn’t really surprising seeing it’s Mother Nature’s own. Thing is to make sure it’s clean. See the comment above from Ray dated Feb 3rd.
    When you say ‘get my top up water to the same levels as my display tank’ you’ll need to go one of two ways – either adjust the calcium etc to the required levels before addition (ie on a routine seawater change) or monitor the levels after the addition. The preferred route (as far as I’m concerned anyway) is the second way – to monitor the aquarium seawater particularly after an addition so that the whole of the gallonage is considered. This happens to be easier as well, as any adjustment to the addition might not compensate sufficiently the main aquarium gallonage and more adjustment could be needed.
    I have never tried using natural sand. The guidelines suggest that sand used for decorative purposes should be coarse so that dirt can be more easily siphoned out. Sand for a deep sand bed (DSB) is more fine, more approaching mud really. Again, the problem could be cleanliness. If the natural stuff is collected and cleaned then any beasties would be mainly lost. The best way in my opinion is to purchase the appropriate grade of sand. If it’s decorative then it doesn’t matter if it contains little life. If a DSB is being used then this can be furnished with life to start with by obtaining live ‘grunge’ (very small rock rubble or sand) from a dealer or a fellow aquarist, it is then able to develop (all things being equal).

  34. Hi John, thanks for replying, still a bit confused
    A) on how to set up ‘trash can’ of top up water re filter, heater etc,
    B) also aquarium will be approx 150gallon, how will I clean the initial fill up water? can I add direct to empty aquarium and run system to clean or will it be better to run 3x 50 gallons individually at 2 days a time before adding to aquarium
    C) when aquarium is full and I have another 50 gallon of clean water in ‘trash can’, do I have to keep this running through a filter or can I turn off and put a lid on it until it is required.
    D) after I have replaced 10% of aquarium water and the cleaned water is added, obviously this will dilute the chemical levels in the aquarium, will this be ok until I get the readings back to the correct parameters
    Thanks again

  35. Hello Phil. The storage container should have a heater (to maintain aquarium temperature), a filter (such as a canister which will need cleaning routinely), a powerhead to circulate the seawater and a cover. The cover should not entirely exclude air, there should be a gap somewhere that permits air to get in/out (this helps with gaseous exchange). Some aquarists also use a UV filter which is designed to assist in the eradication of nasties. The seawater should be in the container with equipment running for at least 48 hours or longer. If possible, when the seawater is run into the container it should be through some filter material to stop some rubbish (if any) entering in the first place.
    The initial aquarium fill is often a little difficult, NSW or not, because of the amount.
    It’s best to run 50 gals at a time in the new seawater bin then move it to the aquarium. There isn’t a need to use the aquarium heaters at this stage as the early amounts will cool down again – unless the aquarium heaters are covered and the aquarium circulators can operate. Run the seawater cleaning operations until the aquarium is full. Turn on the aquarium equipment, heaters, circulators, protein skimmer etc. and run up to the desired temperature. Then turn on the lighting. Allow the system to run for at least 48 hours and check that all equipment is functioning as desired (note: skimmers often fail to operate at full efficiency for a few days, this is probably because of the manufacturing process or a lack of something to skim). When all is proven ok, consider if the biological filtration needs attention (ie. is it live rock or does a filter need priming). Before the biological filtration is activated if needed, tests of the seawater parameters can be completed and any adjustments made.
    When the aquarium is running normally top up the storage bin with a further 50 gallons. Go through the same process but this time when the NSW goes into the bin don’t heat it or run the powerhead, let it stand. At least 48 hours before it is required check if there is any rubbish settled to the bottom of the bin and get rid of it. Turn on the heater, filter and circulator also the UV if in use.
    Ongoing routine testing of the aquarium seawater will indicate if the parameters required need adjustment. These tests are best done after the routine seawater change has been completed. Any parameter change particularly with livestock present should always be gradual, that is any large change should be done slowly.

  36. Hi John,
    thanks for the time you spent with the reply, all ok now, will probably contact you in the future as other questions are bound to come along.

  37. Hi John,
    as far as i have understood, running a sump filter, the flow from my main tank will run into sump through fine mesh filter, through a foam filter, through anti bubble set up, through protein skimmer, through UV Cell and back to tank.
    In bottom of sump will have heaters and calcium reactor.
    I hope I have that correct?
    My next querries are
    A) re live rock, I have understood this as the rock to afix my corals to!, although there are coments on other sites that I should have live coral in my sump as well. I dont know if that is true or not?
    B) re what I listed above for the sump ok, or do I require a bio system as well? as far as I understand this would only be used on a fish only aquarium, or is this also reqired for a reef tank?


  38. Hello Phil. The best rock to use in a marine aquarium is live rock, for two reasons. First, obviously it will set up a reef or some rock decoration. Second, in sufficient quantity live rock will provide the best bio-filtration for the system (in my opinion and also in the opinion of most others). Corals do need rock formations so that they can be positioned securely.
    This takes it to the ‘bio system’ you mentioned. If bio system means bio-filter (some call it life support) then a massive yes, you do need it. All systems need it, without it the livestock will likely die particularly fish! The bio-filtration must be mature, that is the bacteria that do the work must be in place before fish are introduced slowly. Corals present a much lower bio-load. If the bio-filter is missing the livestock, particularly fish, could be poisoned by the production (by the very presence of the fish) of ammonia and nitrite.
    Most reef systems seem to be bio-filtered by a live rock reef, some fish only systems are. An alternative is a canister filter which needs maturing with fluid that is commercially available. Another advantage of live rock is that it will deal, within reason, with nitrate. A canister filter does not and nitrate is not removed (except by routine seawater changes and perhaps a denitrator). I recommend live rock – your local dealer will advise and there is information on this website and elsewhere. The bio-filtration method employed for the display aquarium should be designed to be adequate for the whole system. Any further filtration is simply a desirable addition be it in a sump or not.
    There isn’t any reason to my knowledge why corals should be in the sump. Some aquarists do it, not many as I understand it. Many use algae (such as Caulerpa sp) in the sump to mop up nutrients. With any coral or algae inclusion in the sump then lighting the sump adequately has to be considered. A good many others use a DSB (deep sand bed) as an additional filtration method. There are texts on these on this website and many others. There isn’t an actual requirement to have a sump at all, there are many reefs that do not. They are recommended though as they remove some unsightly hardware from the display aquarium, increase the seawater gallonage and afford a space for further interesting filtration such as a DSB if desired. The inclusions for your sump seem fine.

  39. I live in Kodiak AK myself and a friend are about the only people here that have reef tanks. We are getting tired of being ripped off on artificial salt mixes and worse yet the SHIPPING Charges!!! We are surrounded by NSW. also here is the Alaska Marine Fishers Research Center were they have a large tank with local fish Crabs Ect and a touch tank or tide pool tank for visitors. they do all kinds of research on alaska marine life. I asked an employee there about getting seawater from them the water is pumped off shore from 2 different depths of 60 feet and 90 feet I have a choice of getting raw NSW or filtered SW the filtered water is pumped through approximate 5 feet of sand in a large tower. I picked up 5 gals of it my concerns are it has a yellow tint to it I am not sure if it was my bucket or the water. The water looked clear when it was running but when I got it home I saw the yellow tint I plan on warming it up first and fore most then running it through a magnum filter with carbon. it has some sediment in it which I know the magnum will pull it out. I am spooked over the yellow tint it is testing at 0 nitrate and 420 Cal the ph is 8.0 looking for any help should I be concerned about this color? the sea life here is different but is pristine

  40. Hello Tom.
    The yellow tint of the seawater could be the result of organics and come under the general name ‘gilvin’. The organics are processed by bacteria and could leave the yellow. The usual way of removing the yellowness is with carbon. Activated carbon should leave the seawater clear, once the carbon life is over throw it away. A short easy test for gilvin presence when the obvious tint has gone is to put a piece of white paper at one end of the aquarium and look at it from the other through the seawater. If the seawater is clear, great. The yellow tint is considered harmless but should be removed.
    How fortunate to be close to a marine research centre. There is a Sea Life Centre near to me and they act as a sanctuary for seals and turtles. They also show a wide range of tropical and coldwater life including fish and corals in reef aquariums. They take their seawater from the open sea though I’ve not been fortunate enough to see their filtration system.

  41. do you think it’s advisable to use unfiltered nsw for fish only tanks? i plan on housing only an anemonefish pair in my tank. no corals.

  42. Went today to get 30 gals more of the filtered water I told the guy I get it from about the yellow tint when I got home. He then told me how they clean the sand bed by back flushing it kind of like back flushing a RODI Membrane and that he had just finished doing it . Today’s water was crystal clear I think I will still run it thru my magnum with the carbon filter in it for a couple days

  43. Hello RJ.
    Personally I’d filter the seawater to ‘be reasonably sure’.

  44. Hi Tom.
    Thanks for the update, interesting. Maybe – I’m sure the research station will know – the tint was biologically based before the backflush which would have started everything off again.

  45. I hooked up my magnum with the paper filter I will let it run for 24 hours then put the carbon filter in for the next couple days. I had a small protein skimmer lying around just to see what I get i hooked it up. i am going to look ay all the numbers again just to be sure on sunday I plan on doing water change on Monday I am feeling good about this but wish me some luck

  46. I am getting ready to do a water change and ran into a problem I tested Thursday night and the Calcium level dropped from 420ppm to 370ppm I have been trying to find out why I thought will I tested wrong. So today I went a head and tested again it is now at 350ppm the only thing I have done to this water is heat it to 75.3 and the magnum filter why is the calcium level dropping? Could I have a bad test kit, there is nothing in the bucket to use the calcium, I have added “NO” supplements or any thing else to the water. I have got into trouble before with calcium adding (too much) it was a nightmare I do not understand how the levels can be changing I do not want to add any calcium to this water until I find out if this is possible, and have a understanding of why it is happening

  47. Reasonably raising the temperature shouldn’t have an effect on the calcium. It could be the alkalinity? The measurement for aquarium seawater is in dKH or meq/L and the usual recommended aquarium range is 7 to 12 dKH or 3.2 to 4.5 meq/L*. High alkalinity could result in lower calcium.* The alkalinity affects the amount of calcium that can remain in solution and also resists undesirable swings in pH. When a new mix is prepared from dry salt the measurements of some things could be ‘wrong’ at the start, the seawater is usually left to heat and mix for at least 24 hours before any check measurement is made. May not be the answer but worth checking.
    (* Corals. Eric H. Borneman.)

  48. I’ve been using NSW for years. I also am using sand from the ocean floor. Why not? Pollution is a possibility but so are the various salt mixes on the market.
    I change out 15 gallons each week. All parameters are great. My corals and fish seem happy and occasionally we get either some new food for everybody microscopically or a new addition to the tank via an egg or 2. Its amazing and what we maintain our aquarium for.

  49. I do agree.

  50. i’m a newbie…i have just started my new aquarium 3f w x 5f l x 3f h, it’s quite big aquarium..+-1200-1300liters..i intend to go for NSW for my aquarium..and use natural sea sand..all natural…wish me luck..

  51. Hello Dinodin. That’s quite a large aquarium, bigger than most. As you’ll know you just need to be careful about pollutants of the sea and the sand, especially as it’s going in a restricted volume.
    All the best, perhaps we’ll find out how you’re getting on in a while.

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