There Is A Bad Reading But The System Should Be Mature

Relating to marine aquariums what is meant by ‘mature’? It means that the aquarium system is ready to support life. In fact there are two levels of maturity: the first is the initial level which is achieved after the system has been set up and the biological filter (some call it life support) has been activated. The second is when the system is truly mature, this is when the livestock is present in entirety and the biological filter has fully settled down to the task it faces, this could take many months. The first level could take many days to weeks.

The two main biological filter systems in use are live rock and canisters, the first being the most desirable. The biological filter is populated by bacteria. The bacteria deal with the toxics which, without them, would appear in seawater tests, these being ammonia and nitrite. Ammonia is produced by fish etc as a natural part of life and the bacteria convert ammonia to nitrite and then nitrite to nitrate (depending on the type of filter). In an enclosed system ammonia and nitrite are dangerous and should measure on tests as zero.

It is necessary initially to look at both types of filter separately so let’s start with the canister filter.

The canister filter is an electric pump positioned on a cylinder so that seawater can be moved from the display aquarium through the canister and back to the aquarium. It’s generally best to have the seawater intake at one end of the aquarium and the outlet at the other end, with the returning seawater exiting at the surface (this is to aid with re-oxygenation). As the seawater goes through the canister the bacteria that live on the media carry out the conversion of toxics. When the canister is first set up there aren’t any bacteria present of course. It’s necessary for the aquarist to carefully choose an adequately sized canister then obtain bacteria friendly media (some are better than others) in sufficient quantity. The bacteria have to be introduced to the media and this is best done by the use of commercially available maturation fluid which includes full instructions for use. The procedures are simple and involve regular testing for ammonia and nitrite. The filter is considered mature when readings are zero, indicating that the bacteria are doing their job.

Note that canister filters do not deal with nitrate (because of the presence of oxygen). Some types of media have claimed to be able to deal with nitrate but this ability is usually short lived. To avoid putting undesirable nitrate into the aquarium from the start before livestock are present, put intake/exit tubes into a bucket containing seawater at the required temperature. When tests indicate zero for ammonia and nitrite the filter is ready to support livestock in the display aquarium. The seawater in the bucket should be thrown away. It isn’t necessary to have the filter attached to the aquarium initially: the bacteria are being introduced to the filter media not the aquarium. In the future as the aquarium slowly matures to the second level bacteria could appear elsewhere but it’s the canister media that’s the main home for the hard working bacteria.

Live rock is probably the most used filtration. Not only does it provide the bacteria media, it ‘seascapes’ the aquarium as well. There aren’t any trailing wires or tubes to be seen. All that is required is for the aquarist to purchase sufficient ‘clean’ rock and introduce it to the aquarium making sure that there is good circulation around and, as far as possible, between the rocks. ‘Clean’ (or ‘matured’) rock is that which has been kept for a period by the retailer so that organisms that are dying or dead can be cleared away. These organisms are there because live rock comes from the sea and some of them cannot withstand the stress of transportation. If dying or dead organisms were left they could be a source of ammonia. In addition, there could be undesirable organisms that hopefully will be spotted and removed. If the aquarist is lucky some desirable organisms could survive.

Live rock is able to deal with ammonia, nitrite and in addition, within reason, nitrate (‘within reason’ means there’s a limit). This is because the bacteria require oxygen, those on the surface get it easily and convert ammonia and nitrite but those within the porous rock don’t but still require oxygen – to get it they remove oxygen from nitrate thus breaking the nitrate down.

Ok, so the aquariums set up and there’s a troublesome reading of ammonia or nitrite that shouldn’t be there.

 First of all, with the canister, is the aquarist using that all important requirement patience? The time required for a canister to initially mature varies and the need is to wait until it does. Don’t overdose the maturation fluid thinking that the process will speed up, it won’t. Follow the instructions carefully and stop dosing when indicated, often when the test turns red. What is happening is that the bacteria are building their numbers so that they are able to deal with the toxics present. If the filter media is ok and the pump operating correctly, the bad reading will go, often disappearing in a very short period, sometimes in not many hours. The sequence of readings is usually ammonia, then nitrite, then these clear. Nitrate often appears as the cycle progresses.

If the tests showed zero readings but a bad reading has returned, presumably this is during stocking. Stocking the aquarium starts when the initial maturation point has been reached. Stocking, particularly with fish, much less so with corals (corals present a lower biological load) should be done slowly. After the introduction of two small fish or even just one (in a 50 gallon aquarium) there should be at least a two week period before further fish are introduced, and then just two more, or one if it is larger. The reason is the biological filter has to adapt to the increasing load – if organisms are introduced too quickly the bacteria can’t cope and an undesirable test result is likely. Stop stocking and wait for any bad reading to go keeping an eye on fish already present. If they show signs of discomfort, carry out a partial seawater change. Testing should continue very regularly during the whole stocking period.

If a bad reading appears after full stocking is reached or is being approached and even after waiting it doesn’t disappear, check the canister filter. Is the electric pump working (is seawater coming out of the exit pipe?) They are generally reliable nowadays. Are the inlet and exit tubes properly attached? Is there a blockage preventing correct seawater flow? If no problem is found and the bad reading persists, check the capacity of the canister – manufacturers usually indicate the gallons the canister can deal with. If the canister can’t cope, mature a bigger one (mature the additional media and when ready transfer the media from the smaller canister). Perhaps there is room for more media in the smaller canister. Obtaining the correct size canister is clearly best done at the planning stage.

During maintenance, the bio-media within a canister filter can be cleaned if necessary to maintain seawater flow and general efficiency. The cleaning should be done in warm seawater (the old seawater after a routine change for example). Stir very gently. Never clean in tap water or there will be bad readings on testing!

The aquarist who uses live rock should adhere to the stocking principle outlined above. Some beginning aquarists believe that when live rock is introduced then stocking can go ahead as the rock is fully ready. This is incorrect and could be the reason why a bad reading has appeared.

Live rock is already populated by bacteria, but the adequacy of this population varies. First there are different types of live rock and the amount needed of a particular type should always be checked. Second the rock has to be cleaned as indicated above and in this period the rock lays quietly in seawater without livestock. Therefore there isn’t any ammonia being generated to support the bacteria’s needs and the population could reduce. To counter this, dead organisms could be producing ammonia and it is possible, for a time anyway, that the bacterial count could increase. The clean rock then goes into sale tanks where often it lays without livestock. Again the bacteria population could be decreasing. If the rock lays in a sale tank for a long period the bacteria count could be seriously depleted. It is always worthwhile checking how long since the rock was cleaned. Even with this knowledge the adequacy of the filtration ability of the rock will be unknown, hence the slow stocking.

If a bad reading appears during stocking then stocking any further should be postponed until the reading is correct – in other words until the bacteria can handle the bio-load. If the stocking is nearly complete or fully so and a bad reading appears and does not correct, then it is possible that there is a seawater circulation problem. If a check of the circulation pumps shows no problem then it is probable that the amount of rock is insufficient for the bio-load. Rock as desired should be purchased and introduced and a close watch on seawater test readings maintained. Always ensure that there is adequate seawater circulation when the new rock is introduced and of course that it is stable.

The maximum stocking level relevant to the net gallonage of the display aquarium should never be exceeded.

Generally, with canister and live rock filtration, it’s more likely to meet a problem with a fish only system than a reef one, all things being equal. Why is this? Fish present a higher bio-load to the bacteria than say corals. In a fish only system there are usually many fish for the size of aquarium, and they are all of course fed regularly. In a reef system, as said, the corals present a much lower bio-load and if there are fish present they are often smaller and should be less in number.

It’s not likely that serious problems will appear in a new aquarium system provided the aquarist prepares the system for the bio-load it will contain, that is fish only, a mixed reef system, or corals only. The new aquarist should always display patience, harder to do than might be thought. In a complete system a sudden problem is unlikely if maintenance is properly applied as anything untoward will become apparent in good time, particularly as the aquarist will have gained experience and understand the system thoroughly.

Seawater Parameter Guidelines

Over and over the importance of seawater quality is emphasized. Seawater quality is the number one requirement for the marine aquarium, be this fish only, coral only or mixed reef. Most corals demand light for health and growth, nevertheless seawater quality is still the number one need.

Guidelines are useful for those who are not experienced in the marine hobby, including those who are setting up an aquarium for the first time as they can help towards purchasing the correct equipment such as pumps. They are also useful for those who feel their aquarium is not as it should be, perhaps fish are not as colourful as expected and corals slow to extend and show polyps. There are several reasons why this could be so but the first place to examine is the seawater.

Even if the seawater was at the correct parameters when first used, as soon as it enters the aquarium where there are life forms it begins to deteriorate. This needs to be counteracted by routine seawater changes of the correct amount and at the correct intervals.

As far as the guidelines are concerned, this is just what they are – guidelines not absolutes. The requirement is quality and stability. The guidelines give a starting point and it is up to the aquarist to carry out tests and know the trends of his/her aquarium. The use of a notebook to jot down the results of various tests is recommended, it takes very little time. The notes will indicate the need for supplementation for example, and at what period and amount. Another example is that notes will indicate the effectiveness of routine seawater changing – is nitrate increasing, stable, or perhaps decreasing? Should the amount of seawater changed be increased etc? Once the aquarist has gained experience then the guidelines can be amended if necessary, but always with caution.

Experienced aquarists could run their aquariums at levels clearly different from the guidelines. This could be for various reasons, such as a low SG (specific gravity) to combat certain fish problems. When any particular action is contemplated, always consider the potential impact it could have on other livestock types in the aquarium before proceeding. Research of livestock requirements is always worthwhile.

General guidelines are given for fish only and reef aquariums.

Temperature: Fish only and reef, between 75 and 80degF. As temperature increases oxygen decreases. It could be best to choose a ‘middle’ temperature of 77degF. Some experienced aquarists use a temperature a little over 80degF as this increases the metabolism of the entire aquarium population – again, caution is required.

SG (Specific Gravity): Fish Only, often from 1.020 to 1.022 though it can be higher (and should be if corals are present). There is some suggestion that certain unwanted parasites that afflict fish fare less well at a lower SG.

                                      Reef: normally 1.024 to 1.026.

pH (Potential of Hydrogen). Fish Only and Reef: between 8.0 and 8.4. A pH of 8.3 is often quoted as the ideal reading, and this is generally so, but other readings are acceptable with stability.

Alkalinity: Fish Only, seldom measured unless pH is a serious problem.

                    Reef, between 8 and 12 dKH.

Ammonia: Fish Only and Reef, nil.

Nitrite: Fish Only and Reef, nil.

Nitrate: Fish Only, below 30ppm but always as low as possible.

                Reef: below 10ppm but always as low as possible.

Phosphate: Fish Only, seldom measured unless algae is a serious problem.

                      Reef, undetectable.

Calcium: Fish Only, seldom measured.

                 Reef, Soft Corals – around 375/400ppm. Hard corals – around 450ppm or a little higher. Calcium also assists other life forms such as snails.

Routine Seawater Changes: Fish Only and Reef, 10% of the net gallonage of the aquarium (including sump if there is one) carried out weekly. Even if parameters remain healthy it is recommended that seawater changes continue, though this could be at a reduced level if applied with caution. Remember that seawater changes ‘freshen’ the aquarium and replace trace elements at least partially.

Seawater Movement: Fish Only, around 10 times the net gallonage of the aquarium (excluding any sump).

                                          Reef, Soft Corals – the same as fish only. Hard Corals, around 20 (or a little more) times the net gallonage of the aquarium (excluding any sump).

The guidelines given do not include items such as Iodine, Strontium and Magnesium which mainly apply to reef systems, particularly those stocked with hard corals. With some of these there is argument over how beneficial they could be. For basic purposes such inclusions generally confuse matters.

If the aquarist maintains basically high quality seawater and applies other necessities correctly, for example lighting and seawater movement the aquarium display should be beautiful. Additional considerations, if any, arise as experience grows and the trends and needs of the aquarium become known.

Seawater Changing – Always The Same?

 

As has been repeated so many times before, seawater quality is the number one requirement for a successful marine aquarium. Having said that, is there any variation on the change regime?

For a new marine aqurium the guideline amount to change is 10% of the net gallonage weekly. A new aquarium needs time to settle down, or to put it a better way, to stabilize. This period can vary and during this time there is a requirement to carefully monitor conditions by testing.

Marine systems don’t follow one format, they can have different equipment fitted and different inhabitants. This is the heart of the matter really, the type of aquarium.

Let’s go back a bit though. As said, there is an initial guideline of 10% for seawater changing. This should be adhered to in the early days of the aquarium and at the same time seawater quality testing should occur. This testing at its base should include specific gravity (SG), temperature, ammonia, nitrite, nitrate and pH. What is being watched for is reasonable stability and acceptable levels of toxics. Once the system is initially mature, that is ammonia and nitrite have disappeared, nitrate will usually make an appearance as the end product of ammonia/nitrite conversion (this doesn’t always occur but that will not be gone into here). Nitrate needs to be kept low in any system, but the guidelines are for a reef less than 10 ppm (parts per million) and fish only less than 30ppm, though the latter should be as low as is possible as well.

Seawater changing should continue until there is an indication of the rate of rise in nitrate. It is very good practice to jot down in a notebook the nitrate level at each test, in this way eventually the rate of rise can be predicted.

Once the aquarist has knowledge of the nitrate trends then consideration can be given to seawater changes. If the nitrate contiunues to rise but more slowly, then an increase in the amount of the seawater change can be considered (and also a check made of the feeding regime, to avoid overfeeding). If the nitrate has not increased but is stable at an acceptable level, then the change amount is seemingly adequate. If there isn’t a nitrate presence, then it is possible to reduce the seawater change amount. However, in this case take into consideration the fact that a change not only controls the nitrate, which is used as an indicator, but also replenishes to a fair extent trace elements, and others such as calcium. It could be best to continue at the guideline amount.

There are mainly three kinds of saltwater aquarium systems: the fish only system, the mixed reef (fish and corals) system, and the corals only system. At a guess the most popular is probably the mixed reef, followed by fish only then corals only. Should the seawater change be the same for all three?

It is generally thought that the heaviest nitrate probability is with the fish only system. This is because these have the greatest number and/or size of fish present, and fish require feeding more. It follows that the mixed reef is the next in line for nitrate, followed by the corals only system.

The same guideline applies to them all, 10%. It is likely that this will be excessive or adequate for a coral only system, with that possibility reducing for a mixed reef and much reduced for a fish only. Again, the same action can be taken in response to ongoing test results.

So it is clear that there isn’t a rule for seawater changing. The guideline of 10% is for the early months as the aquarium matures and trends are discovered. Following this, the aquarist can make a reasonable determination on ongoing action.

Routine seawater changing should not be abandoned or over extended even though tests indicate it could be. Seawater changing is of great benefit to the health and vitality of the inhabitants. There may be equipment fitted such as a protein skimmer, but such equipment is an aid to seawater quality and not a guarantee of it.

Why Should Alkalinity Be Higher In The Aquarium?

The marine aquarium can be so beautiful if the aquarist does straightforward routine maintenance as required, and doing this maintenance includes attention to the all important seawater quality.

Seawater quality is maintained by routine changes of sufficient quantity, and at the same time tests are completed to ensure that the required standards are met. These tests include specific gravity (SG), pH, nitrate and for a reef could include calcium and similar. Some aquarists continue to test for ammonia and nitrite after the initial maturing process. Alkalinity is a test that is useful to marine systems too.

It would seem fair to think that Mother Nature would know best in these matters and the alkalinity level in the wild is 7 to 9 KH*. So perhaps we should keep out aquarium seawater at the same level.

We could maintain a natural level and hopefully all things being equal there wouldn’t be any problems. However, we are not talking of the vastness of the seas and oceans where seawater quantity is measured in cubic miles; we are talking about aquariums where even a large home system of 500 gallons is, by comparison, very tiny.

Most aquariums are fully stocked whatever system they are. The life in the aquarium puts pressure on the seawater in several ways and one of them is the acid/alkalinity balance. We know this measure as it uses the pH scale, and we want a pH of between 8.0 and 8.4 which is on the alkaline side. The life functions in the aquarium constantly try to reduce this pH towards the acid side, something we do not want.

Prevention of the reduction in pH is achieved by the ‘buffering’ capacity of the seawater, in other words its ability to resist changes caused by acidic substances. The ‘buffer’ is mainly the carbonate/bicarbonate content of the seawater. In certain circumstances the buffer could be seriously weakened or even exhaust and the pH would fall which is detrimental to the livestock.

Dry seawater salt as purchased by most aquarists for seawater make-up has a buffering capacity usually around natural levels. However, many aquarists boost the buffering capacity of their seawater by adding carbonate/bicarbonate powders. These powders are usually mixed in some seawater before being added to the aquarium, being careful not to hit corals etc. The powders are sold commercially and are very easy to use.

In an aquarium it is considered best to maintain alkalinity from 8 to 14 KH.* It is not recommended to raise the level above 14 KH.* The recommended level of 8 to 14 KH does not mean the level can vary within these limits, it should be reasonably stable at the chosen point, ‘reasonably’ meaning that some variation over say a week will not usually be harmful. My system runs at 10 KH and needs boosting to an extent weekly.

If the aquarist measures the alkalinity of a fully stocked system on a weekly basis and keeps a note, then the trend of the aquarium can be seen. The amount of buffer that needs to be added is easily prepared week to week. Testing can be reduced once this requirement has been discovered but should not be abandoned.

If pH is a problem and it is falling despite routine seawater changes and good husbandry in feeding etc, then perhaps the buffer capacity needs attention. Increasing the buffer by 1 KH week to week will not do harm. I have found a good alkalinity level is also beneficial to the growth of welcome encrusting algae which can beautify the aquarium.

By the way, if the desire is to measure alkalinity by mg/l, then multiply KH by 17.9.

(*Reference: Marine Atlas. Helmut Debelius & Hans A. Baensch)

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I Know About Seawater Quality, But…

Marine aquarists aim to maintain seawater which is of the highest quality. The reward for doing so is a vibrant aquarium, be it a fish only, corals only or mixed reef, and without the intrusion of nuisance algae.

‘Quality’ means the seawater is stable, the pH in the region 8.0 to 8.4, nitrates in a fish only at 30 ppm (parts per million) or less, in a reef system 10 ppm or less, and phosphate preferably undetectable. If the aquarium contains a captive reef the aquarist will quite likely maintain alkalinity, also calcium if this is relevant to the livestock. However, for the purposes of this discussion quality means stable pH and ‘proper’ nitrate and phosphate levels, that is, they are within the guidelines.

Aquarists complete routine seawater changes which go a long way towards maintaining high quality. Any undesirables in the seawater are diluted and, at the same time, trace elements are replenished or partially so. The seawater could be said to be freshened. The initial guideline amount for routine changes is 10% of the total net gallonage of the system weekly. This therefore includes any sump. There isn’t any requirement to change 10% every week; the aquarist could find it more convenient to change 20% fortnightly. However, a weekly change probably contributes to stability in itself, as the change caused by raw seawater being added is smaller.

pH as said could be anything between 8.0 and 8.4. Whichever the measurement is it should be reasonably stable. It is possible, in some circumstances probable, that there will be a fluctuation in pH between the lights on and off periods. This is normal as it has to do with seawater dissolved gas levels. If there is an excessive reduction, or any reduction which worries the aquarist, one way of combating the change is to employ algae in a sump. The macro algae Caulerpa is commonly used and is lit by fluorescent tubes which have an opposite cycle to the display aquarium lights, which means that when the display aquarium is lit the sump is not and vice versa. Plant growth tubes are often used to assist the Caulerpa, these tubes have a lower Kelvin rating than lights commonly used on a display aquarium. The Caulerpa will also act as a natural filter to combat nitrate and phosphate.

Sometimes pH is not varying excessively, it is just too low. If the reading is consistently too low, and by this it is meant below 8.0, then it is possible that the system does not have efficient enough gas exchange. Gas exchange occurs at air/seawater interfaces, particularly at the aquarium surface. It also occurs on protein skimmer outlets, weirs and the like. It is at these interfaces that the seawater takes in oxygen which is clearly important for livestock. Too low an oxygen level could have serious repercussions for the livestock under certain circumstances, and it could also be the cause of a low pH reading.

Testing the seawater for sufficient oxygen relevant to pH is very easy. Measure the pH of the seawater in the aquarium and make a note of the result. Siphon a gallon or two of seawater into a safe bucket, the one used for new seawater will do. Importantly maintain the temperature so it is the same as the aquarium and also circulate the seawater vigorously for two hours or so. The heater used for new seawater will be fine, also the powerhead or air pump. Note that the seawater needs to be moved vigorously, if it is sluggish it will not do.

After the required time measure the pH of the seawater in the bucket. If it is the same as the aquarium then seawater movement in the aquarium should be adequate. If the pH is higher than that in the aquarium then increasing seawater movement in the aquarium should be beneficial. Sometimes an additional powerhead will do. Place it about half way down in a convenient and hopefully hidden from view spot, and point the outlet at the surface or at an angle across it. Seawater will be moved either in a mound at the surface or a stronger flow will move across the surface. In either case gas exchange should increase affecting the pH. Before an additional powerhead is used it could be worthwhile checking the positions of existing devices.

If the pH is too low and the above test doesn’t make any difference, maybe the alkalinity is also too low. Keeping it brief and basic, seawater is on the alkaline side of the pH scale. Life actions of livestock continually try to push the pH towards the acidic side, particularly in heavily stocked fish only systems. Increasing the alkalinity could maintain pH at a more desirable level and is worth trying. If alkalinity is adjusted it is usual to keep it above natural seawater levels. If it is intended to try this, then there isn’t any mystery or need to explain measurements. Test kits and adjustment powders are commercially produced and easily obtained. The instructions will explain all and there will be a measurement chart included.

The aquarist could be having trouble with nitrate and/or phosphate. If routine seawater changes are properly done and excessive readings persist there are checks that should be initially considered.

First is feeding as this is the major culprit in many seawater quality problems particularly with novices. Nitrate is a product of the nitrogen cycle and is the end product with a canister filter. Even the acclaimed live rock cannot deal with some nitrate readings. Phosphate is mainly introduced to the seawater by feeding. Both nitrate and phosphate have been implicated in problems with nuisance algae, so excessive readings need to be reduced. There is information on feeding techniques in the Articles section on aquaristsonline.com, so further explanation will not be given here. The tendency to overfeed usually has two causes, the first being the pleasure of feeding and the second the concern that the livestock get enough. Both are good reasons, but the act of overfeeding will do harm. As said, the first action is to carefully check the method of feeding and the amount fed.

Nevertheless, some aquarists have trouble anyway, despite being disciplined when feeding and despite doing regular seawater changes. It has already been stated that the initial guideline for routine seawater changes is 10% of the total system net gallonage. Note the word ‘initial’. It may be that the amount changed needs to be increased. It could very well depend on the livestock load. A fully and correctly stocked mixed reef system will usually have a lower bio-load than an equivalent sized fully and correctly stocked fish only system. Fish present a heavier bio-load than corals. So for example in a fish only system there is heavier feeding because of the higher number of fish and of course the fishes life cycles continue. Thus there is more scope to see excessive nitrate and/or phosphate readings. The answer here is probably dilution. In other words an increase in the amount of seawater changed routinely. If the aquarist is changing 10% this could be increased to 15%. Have the readings begun to subside? The readings will gradually subside, as additional pollution continues to be produced – it will not suddenly or quickly disappear. If not, try a further increase to 20%. It is not normally recommended to change more than 25%.

It has to be reiterated that increases in the gallonage of routine seawater changes come after the aquarist is fully satisfied that other avenues to solve the problem are exhausted, such as the mentioned feeding. It is also important to examine carefully the filtration which in the first instance should be adequate. Filtration to combat nitrate and phosphate could be increased. In the case of nitrate more live rock for example, and/or if there is a sump the introduction of a DSB (deep sand bed) and perhaps some Caulerpa algae. In the case of phosphate perhaps an anti-phosphate resin filter could be considered.

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What Salinity Should I Keep My Marine Aquarium At?

Marine aquarists use a hydrometer to measure the specific gravity (SG) of the seawater. The hobby hydrometer is not a pure scientific instrument but is capable of sufficient accuracy to enable stability of the SG – provided the aquarist does at least a weekly check.

Marine aquariums come in two main types, fish only and reef. To be precise, for ‘reef’ I should really say mixed reef and corals only reef, the former being corals and fish (the usual).

The first consideration is what SG is really necessary. To answer that it would seem best to look at the wild reefs, our livestock’s natural home. The SG of the sea in those locations should give the answer. Well, yes it should, but it doesn’t seem as simple as that. Is it ever!

The sea is considered to be stable which for the volume taken up is not really surprising. The SG on the reefs though is perhaps surprising, as it can range from 1.017 to 1.031*. Specific gravity is affected by temperature and some variance in temperature is understandable. In addition, some seas are more ‘land-locked’ than others such as the Red Sea. So there is going to be variance.

Some state that it is best to mimic nature and I sympathize with that. However, mimic which reading?

Looking at averages could be the answer. The lowest encountered salinities (on reefs measured) had an average of 1.025, and the highest 1.026*. Now this is more like it.

Provided livestock are acclimatized properly there is tolerance to some change which over a period becomes the normal. Generally, fish are like this and will happily live in seawater with an SG from 1.022 to 1.026. (Some aquarists use lower SG levels for specific purposes.) There seems little point in having a higher SG than necessary so many fish only systems run at SG 1.022. There is some evidence that certain parasites don’t do so well at 1.022 so that is a bonus. Also, and very much secondary, not so much dry salt will be required for routine seawater changes which will reduce costs a little.

What of the reef system? Whether this is corals only or mixed, the corals dictate the SG requirement. Corals are much less tolerant of a lower SG and 1.024 is the minimum for them. The range usually cited for corals is 1.024 to 1.026.

Whatever the seawater SG is, it should be stable. Testing at least once weekly is required and unlike many other types there will not be a need to renew a test kit from time to time. The hydrometer, barring accidents, is a once only purchase.

SG is a very important parameter of seawater and one that is very easily controlled. The SG could reduce because of salt ‘creep’, where salt encrusts overhead wiring, lights, glass and the like. The SG could increase because of poor seawater top-up management, as only fresh water evaporates leaving the salt behind. High quality seawater is the often quoted number one necessity and simple monitoring is required.

(*Reference: Aquarium Corals. Eric H. Borneham)

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The Constituents Of Seawater

The seas and oceans cover the majority of the planet surface. Within those seas the wild reefs have grown and all of their needs are met, be that calcium or whatever. The life on the wild reef has had a very long time to adapt to the sea, which is considered to be stable.

Some of these life forms end up in the home marine aquarium. With the natural seas being so stable it follows that for success the conditions on the wild reef should be duplicated as near as possible, and conditions provided that successfully permit life to function and be healthy.

Seawater quality is the number one on the list of ‘must haves’ for success so it follows that the seawater used should be as close as possible in make-up to the natural kind. In much earlier days aquarists would obtain some constituents – not all of them by any means – from a chemist and mix up a brew. Livestock existed in this fairly well for a while but trouble usually appeared. Nowadays there are many high quality dry salt mixes available which the manufacturers state equals the natural type. Be that as it may, the appearance of these dry salt mixes has brought the successful maintenance of a marine system within the reach of every aspiring aquarist provided the interest in the hobby is maintained and the requisite maintenance is done.

Seawater is a mix of many things, some of them present in major amounts, others in trace amounts, and more with a very tiny presence. So for the benefit of anyone interested there follows a list of the make-up of seawater. There is clearly no requirement of any kind for an aquarist to know them but as said it may be of interest. It could also be of use for aquarists who wish to maintain natural levels of important parts such as calcium etc.

Major Elements. (All measurements in mg/l)

Chlorine	18880
Sodium	10770
Magnesium	1290
Sulphur	884
Calcium	412.1
Potassium	399
Bromine	67.3
Carbon	28
Nitrogen	15
Strontium	7.9
Boron	4.5
Silicon	2
Fluorine	1.3

Trace Elements. (All measurements in ug/l)

Lithium	180
Rubidium	120
Iodine	60
Phosphorus	60
Molybdenum	10
Zinc	4.9
Argon	4.3
Arsenic	3.7
Uranium	3.2
Vanadium	2.5
Aluminium	2
Barium	2
Iron	2
Nickel	1.7
Titanium	1
Copper	0.5
Cesium	0.4
Chromium	0.3
Antimony	0.24
Manganese	0.2
Krypton	0.2
Selenium	0.2
Neon	0.12
Cadmium	0.1
Wolfram	0.1
Cobalt	0.05
Germanium	0.05
Xenon	0.05
Silver	0.04
Gallium	0.03
Lead	0.03
Zirconium	0.03
Bismuth	0.02
Mercury	0.02
Niobium	0.01
Thallium	0.01
Thorium	0.01
Tin	0.01
Hafnium	0.007
Helium	0.0068
Beryllium	0.0056
Gold	0.004
Rhenium	0.004
Lanthanum	0.003
Neodymium	0.003
Tantalum	0.003
Yttrium	0.0013
Cerium	0.001
Dysprosium	0.0009
Erbium	0.0008
Ytterbium	0.0008
Gadolinium	0.0007
Praseodymium	0.0006
Scandium	0.0006
Holmium	0.0002
Lutetium	0.0002
Thorium	0.0002
Indium	0.0001
Terbium	0.0001
Samarium	0.00005
Europium	0.00001
Radium	0. 00000007
Protactinium	0. 00000005
Radon	0. 000000000006

Constituents with a tiny presence.

Technetium

Ruthenium

Rhodium

Palladium

Osmium

Iridium

Platinum

Astatine

Francium

Actinium

(Reference: ‘Baensch Marine Atlas’. Helmut Debelius & Hans A. Baensch)

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