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 Flow, It Matters

Corals have definite preferences for seawater flow. Some, such as many hard corals, prefer high flow and others, including many soft corals, prefer a lower flow. The general guideline for seawater flow with a soft coral display is 10 times the net seawater gallonage per hour, and for SPS corals 20 times or more.

There are different types of flow and basically the one type that should not be striking corals is laminar, or flow moving in a straight line. The type of flow required is turbulent, another way of describing it is chaotic. This flow brings food to the corals and helps remove waste.

I run a soft coral aquarium, it has been running for just over eight years now. I prefer soft corals as though they aren’t quite so ‘reefy’ they move in the flow and have some lovely pastel colours. In the top area of the aquarium the current is quite strong but lower down it is considerably less.

The display includes ‘mushroom’ corals, I believe them to be Ricordea species (though I’m ready to be corrected!). They prefer a lower seawater flow so that they can expand fully. The photo above shows these, though they are the ones that have colonised an area that is in higher flow seawater. They measure around 3 inches diameter (circa 7.5cm) and are clearly being effected by the flow – their edges ripple and lift. Therefore the mushrooms have minimized the effect the flow has on them by keeping their size down.

The photo above shows one of the original mushrooms that has been placed in a low flow area. This time there isn’t a problem with seawater flow, the coral has expanded to a considerbly larger diameter, about 7 inches (circa 18cm). Though the coral edges and surface do move a little it is not particularly significant. The coral is also free to take up different postures, sometimes with an undulated surface and sometimes with an upturned edge. This wouldn’t be possible with stronger flow.

So to get the best display from a coral it needs to be in the area it prefers and has adapted to in its natural habitat. All that is needed is a little research on seawater flow and lighting needs.

Are There Any Disadvantages In Using Reverse Osmosis Water?

Marine aquarists, particularly those running a reef aquarium, in the main tend to avoid the use of tap water. This is because tap water quality varies quite a lot depending on where the aquarist lives.

In agricultural and/or industrial areas the water may be affected by nitrates, pesticides, heavy metals and the like. In addition bacteria, viruses and spores (example fungal) could be present though these are much more unlikely.

Water authorities have to be sure that the water is safe for human consumption and therefore abide by standards set down for the maximum amount of any substance that can be present. In addition after treatment the water is kept clean by the use of chlorine. Chlorine also helps keep the delivery pipe work clear of bacteria etc. Chloramines are sometimes used on occasion, when a controlled amount is pumped through the pipes for cleansing. In some areas fluoride is mixed into the water as it is said (not without argument) that it is good for teeth.

The tap water may be fine for us humans but we don’t want any of the ‘extras’ in our aquarium seawater. What we want is seawater that is as pure and natural as possible. Dry sea salt is not cheap and it is not logical to pollute the carefully balanced mix with ‘polluted’ tap water.

95%+ pure fresh water from the tap is achieved by using a reverse osmosis (RO) unit. There are other ways but the RO unit is probably the best way for aquarists. Tap water pressure is used to force water through a sediment filter (this is not always present), then a carbon filter where chlorine is removed (chlorine is very detrimental to the next stage), then through a membrane where very nearly only pure water can pass, unwanted substances cannot. Some RO units also incorporate a final cleaning stage using exchange resins, where any final pollutants are removed. This final stage is not absolutely necessary.

So that’s the answer for the aquarist wanting to mix the highest quality seawater, use an RO unit.

Hang on a minute though, there’s usually some kind of disadvantage.

There is and with the RO unit it isn’t really cost as it can be with some equipment. RO units that are well made and functional are available at reasonable prices. It isn’t locating the equipment either as an RO unit can be hidden away in a cupboard close to an incoming water main, placed under the sink, in fact placed anywhere as long as a mains water supply is within reach and there is space available for a collection bucket. There isn’t a cost disadvantage in using the RO unit as with heaters or metal halide lights as they are not electrically driven. Maintenance is usually wide spaced and not a problem (maintenance requirements are subject to the amount of water passed through the unit and the condition of the tap water before treatment).

The disadvantage with the RO unit is linked to performance. This isn’t to say that they are inefficient, far from it, at least as far as the quality of the useable water is concerned. It is the water that is unusable that is the disadvantage.

When an RO unit is connected to the mains water it produces two outputs. One is the purified water (the permeate) that the aquarist collects to use in new salt water mixes and for evaporation top-ups. The other is the unwanted water (the concentrate) that contains all the impurities (solutes) that could not pass through the membrane. The ratio of concentrate to permeate is about 4 to 1. In other words, for every 4 gallons of unusable concentrate there is 1 gallon of useable purified water.

Some aquarists are not too keen on this ‘waste’. However, it is a straightforward exercise to arrange collection of the concentrate in a larger container. The container need not be of high (food) standard as the water inside will not be used for any human or aquarium related purpose. It could be used when needed in a garden for watering, as an example. With a small aquarium the required amount of purified water and therefore waste water may not be seen as a problem, but with a much larger one it depends on the attitude of the aquarist.

The advantages of using purified water from an RO unit for marine aquarium purposes have I think been well demonstrated.

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Aquarium Water Is Just Water Right – Wrong!

When keeping an aquarium – be this coldwater, freshwater, marine etc then there is one thing you are definitely going to need other than the aquarium – water!

Sound obvious doesn’t it?

Well let’s face it if we don’t put water in the aquarium nothing is going to survive is it – it’s not as if you can fill it with custard!

But water is just water – isn’t it?

The answer to this is both yes and no. It is correct that water is just water in the sense that it is wet however the substances which is in the water is what makes the water we want to use in our marine aquariums different.

In home water various additional substances are added to it in order to make it safe for human consumption and also various other aspects which get into the water by, for example, agricultural practice (phosphates, pesticides, nitrate etc).

It is for this very reason that the majority of aquarists use reverse osmosis water.

There are various other techniques which people also use – natural sea water, deionised water etc, however normally reverse osmosis is the water of choice for the majority of saltwater aquarists.

So what is reverse osmosis?

Basically a reverse osmosis unit is a device which is attached to the home water supply and this water is then pushed through a semi permeable membrane with pores so small that only water will pass through. It then also passes through other chambers where the majority of other substances are removed.

Generally the reverse osmosis process is 95% or higher in efficiency. The end result of the reverse osmosis process if water which is safe for aquarists to use in their saltwater aquariums.

There are a couple of things which need to be noted about a reverse osmosis unit however.

The first is the waste that a reverse osmosis system creates. For every five gallons of water pushed through a reverse osmosis unit, normally 4 gallons or so will go to waste. There are various factors which reduce the wastage in a reverse osmosis unit, the main one being the amount of calcium in your tap water. It has been noted that aquarists with soft tap water get a higher volume of usable water to waste ratio than those with hard water.

The second is chlorine. Chlorine is harmful to the membrane which is at the heart of the reverse osmosis unit. For this reason activated carbon chambers are provided for the tap water to pass through before the membrane is reached. These are normally called pre-filters or micro-filters. This pre-filter does require changing based upon the manufacturers recommendations. I recommend that you adhere to these recommendations as replacing the membrane will cost more. In a lot of instances, dependent upon the make and model of reverse osmosis unit purchased it is sometimes more cost effective to purchase a completely new unit.

The third is that the reverse osmosis membrane must constantly remain wet. If the membrane is allowed to dry out then it will become brittle and not function correctly. If this is allowed to happen all you will effectively be doing in sieving the water not purifying it.

Reverse Osmosis devices can be purchased nowadays for very reasonable prices and are available in numerous sizes. Size is normally determined in how much water is processed per hour, therefore a 50gph unit will create 50 gallons of reverse osmosis water per hour when used in optimal conditions.

It is definitely worthwhile investing in a reverse osmosis unit if you have a larger aquarium as the initial water fill and subsequent water changes will require more water, however for aquarists who have smaller aquariums it may not be cost effective to purchase a unit. Fortunately a lot of pet shops are now selling reverse osmosis water so if you have a smaller aquarium then it might actually be cheaper to simply purchase you water from your local fish shop.

As with anything in this hobby the unit does need to be maintained. It does not require a lot of maintenance but the pre-filter on the device does need to be changed at regular intervals. This is normally determined by the manufacturer and I would recommend that you follow their recommendations.

Another thing that I normally do is occasionally test the water from the r/o unit. I test both for nitrate and phosphate to ensure that the unit is running at optimum efficiency.

Another method which aquarists use is to test for total dissolved solids. Meters can be used for this which you can use to test the water produced. You can also purchase inline TDS meters which attach to the reverse osmosis unit. Some reverse osmosis units have these devices fitted.

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Why You Should Use Reverse Osmosis Water

Fresh water is used constantly by the marine aquarist, first when the aquarium is initially filled and then for ongoing routine water changes. Of course, an appropriate amount of dry salt mix is added. Fresh water is also used for evaporation top-ups.

On the face of it using tap water seems reasonable – but is it?

Tap water is prepared for human use, and is safe: children and adults use it for drinking, cleaning teeth, showering etc. There are regulations about the minimum condition the tap water should be in, and the water authorities adhere to this. But…

Tap water has levels of nitrate, phosphate, insecticides, heavy metals, chlorine, chloramines etc that the marine aquarist could well do without. In other words, tap water isn’t just pure water. The unwanted parts vary according to area. Some agricultural areas could have higher nitrate and insecticides etc, and other areas could well have higher levels of heavy metals and the like. Water companies tend to add chlorine and chloramines as a matter of course.

Seawater quality is very important in a reef system and also in a fish only system. By using tap water the aquarist is adding items that are known to be a potential problem – nitrate is an obvious example. There is a method that is easy to use and solves the ‘contamination’ problem easily.

This is the reverse osmosis (R/O) method. This is were a filter, the R/O unit, is connected to the tap water supply, the tap water slowly flows through the filter, and the purified water is collected in a bucket. It really is as simple as that.

Reverse osmosis filters come in a range of sizes, with varying outputs. The output is often given as gallons per day, and the aquarist needs to choose one that will produce enough water for a routine water change (the initial fill of the aquarium is usually ignored as this will normally only be done once. R/O water should be used though).

The filter has stages, and the first is normally anti-sediment, which protects the later stages from clogging. Then comes an activated carbon stage, where chlorine is removed from the water. This removal is important as chlorine degrades and eventually could spoil the R/O membrane. The R/O membrane is the final stage- the membrane is very fine, measured in microns, and will only allow pure water to pass. Once the water has gone through these three stages it will usually be 95 to 98% pure.

Some R/O filters have a fourth stage, where the purified water goes through a special granular mixture. This gives the water a final clean. The fourth stage is not essential, but it does further increase the purity of the water.

Not all the tap water that reaches the filter will be purified, about one part in five is. There is some small variation on this. The water that gets to the storage bucket is ready for use, but the other four fifths or so is discarded along with unwanted contaminants. This latter water could be collected for use in a garden or similar if wanted.

The purified water that is in the collection bucket is ready for salt to be added to prepare a routine water change, or for use as a top-up to replace aquarium evaporated water.

There is a further reason why R/O water should be used, and that is to do with the dry salt that most aquarists use. Commercial salts nowadays are of a very high standard because the manufacturers make every effort to produce a properly balanced mix without contaminants. In fact, many manufacturers trumpet this fact by adding wording to the salt pack such as ’No Nitrates, No Phosphates’ or similar. So why add contaminants by using tap water and negate, even partially, the purity of the salt?

R/O filters do not cost a lot and are readily available. All they require is a tap water supply and normal mains pressure. The manufacturer’s advice on maintenance, which doesn’t amount to much, should be followed.

By using R/O water the aquarist is ensuring as far as possible that the water that is put in the aquarium is of the highest quality, and it is highly recommended.

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Water Movement In The Display Aquarium

Both the reef aquarium and fish only aquarium have certain demands that are very important. Top of the list is water quality, followed by lighting (for a reef anyway).

Water quality is of course measured, and for both types of aquarium the four basics are the same – ammonia, nitrite, nitrate and pH. With the reef the list is extended, taking into account for example alkalinity, calcium, magnesium etc.

Water quality is more than measurement however. Though a personal thing, I count water movement as part of quality. Water movement brings oxygen and food to corals, and helps removes dirt and mucus from them. It ensures fish have sufficient oxygen, and also makes them feel more ‘at home.‘ It also oxygenates a reef and assists in keeping it clean. The seawater is ‘clean’ and freshened in all parts of the aquarium. With good water movement the very important gas exchange is achieved – water is continually delivered to the surface to re-oxygenate.

Plenty has been written on this subject, and on this website, already about water movement and its creation. The methods are generally straightforward.

However, I suspect that many aquarists, particularly newcomers, look at water movement as circles. There’s the aquarium, and the guideline suggests water movement of, say, 10x the net gallonage per hour. Easy! Get a couple of powerheads which pump that amount of water, or somewhere near, and the job is done.

If suggestions have been understood, the powerheads are placed strategically to create chaotic and random water movement. Still well and good.

It is thinking ‘in circles’ though. Perhaps it would be better to say thinking ‘horizontally.’ No matter how carefully the powerheads have been placed the seawater cannot possibly reach all parts of the aquarium with good movement. All aquariums have quiet areas where corals that prefer calm can dwell.

So the aquarium is equipped with what seems to be sufficient power to move the water. Probably it is.

What about the ‘vertical’? No, I don’t actually mean pump water vertically in the aquarium, I mean deliver water low down from higher up. What about one additional powerhead that is in an accessible position but pumps water through a tube to, say, a spray bar behind the lower reef or even under it. There are different ways of delivery. All the powerhead needs is a sleeve on the intake (sponge or similar) to stop debris and that’s it. Maybe two powerheads would be required. Whatever.

The aquarist can then be more sure that water quality is high everywhere, with the benefits that can bring.

Advanced systems can use carefully designed closed loops, where the water outlets are positioned in strategic places to ensure fully advantageous delivery. The ‘ordinary’ aquarist need not go to these lengths unless really desired. The use of additional water movement devices, one or maybe two, will do a fairly similar job at a very reasonable cost.

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Do You Have To Use Reverse Osmosis Water?

Reverse osmosis (R/O) water seems to pop up very regularly in questions and discussions. Some aquarists consider the R/O filter to be another piece of equipment that is not really necessary. There is quite a bit of confusion particularly with beginners, which is understandable when the whole spectrum of equipment and guidelines for keeping marine systems is considered.

The heading question can be answered straightaway – no, you don’t. If you’re lucky, and have a water source such as a well that provides water of high purity, or live in an area where tap water is of a really high standard and not polluted with nitrates, insecticides, metals, bacteria (I won’t go on) then the tank seawater mix could well be of high quality.

Some aquarists have tried using bottled spring water and found that the purity was in fact not as thought and/or the cost was prohibitive. Similarly, some have obtained a supply of distilled water from a chemist or other source and tried that. This proved to be an inefficient way of obtaining the amounts of seawater – multiple gallons – often required, plus the cost.

A few other aquarists have turned to Mother Nature, a fine choice provided the transportation and storage needs can be met, and an unpolluted source can be found.

So for the majority it is the household tap. The water from the mains tap is purified and regulations exist for the amounts of pollutants that are acceptable. Nitrate can be present in a surprisingly high amount, as can phosphate, plus the insecticides etc mentioned earlier.

The water from the tap at the very least should be tested for nitrates and phosphates before consideration is given to using it for a salt mix. If tests are not done then the aquarist is possibly preparing a potential home for nuisance algae, particularly if high power lighting is being used. Added to the pollutants in the tap water are the natural developments in the tank because of the natural processes of the livestock, and the results of potential overfeeding.

Personally, I find it difficult to follow the logic (should I say illogic) of not using R/O water. First, look at the expense the aquarist has accepted in preparing the aquarium system, having purchased lights, salt mix, test kits, a protein skimmer, canister filter, heater(s), circulation pumps, maybe a calcium reactor etc, and also of course the aquarium and stand. Then there is the internal decoration, such as live rock and maybe sand. The fish and corals haven’t been mentioned yet! Whether a fish only or reef system, it all represents a fair sized investment.

Over and over emphasis is placed on the need for high quality water. To this end, the dry salt mix that most aquarists use is manufactured to a high purity, lacking in such unwanted substances as nitrate and phosphate. Why add less than ideal water to it?

If there is a marine retailer close by, R/O water may be available to purchase by the gallon. Quite reasonably, the retailer has to make a profit. Moving the water in containers is not the easiest practice.

If the aquarist purchased an R/O filter then production of purified water would be straightforward and predictable demand easily met. The cost of the filter, particularly when the cost of other items of equipment is considered, is reasonable.

R/O water is generally 95 to 98% pure and the environment for the aquarium livestock would be enhanced, which is probably the most important point, and the possible appearance of undesirable headache algae would be reduced.

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