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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Diatom Algae

Algae! Now there’s a word that can raise very mixed emotions in a marine aquarist. Even if the aquarist is a newcomer to the hobby, if plenty has been read in research he or she will be aware of the dangers.

Of course not all algae’s are bad; in fact they could be the aquarist’s friend. There are many forms of decorous algae. Caulerpa is a larger form of algae that is often used by more experienced aquarists to reduce nitrate and phosphate, as it uses the nutrients for its growth which of course means that other nuisance algae cannot. When used this way it is usually kept in the sump under individual lighting.

The algae types that worry aquarists the most are green filamentous and smear algae. Filamentous green algae take the form of very thin strands which are close together and could be up to 8″ (circa 20 cm) long. If unchecked it could cover all the rock and sand. Smear algae, also known as blue-green algae (though it comes in more than one colour variation), properly known as Cyanobacteria, which is often a dark reddish brown appears, as the name suggests, as a thin covering that is really unsightly. If unchecked this thin film could extend over much of the aquarium décor and smother all underneath.

There is another algae type that often causes alarm and it often appears in a newly set-up aquarium, seemingly – from anecdotal reports – particularly where a decorative sand bed (or possibly a deep sand bed) is in use. It is not a definite appearance however; quite a few aquariums never develop it. It could be a nuisance in older aquariums under certain conditions.

This algae is diatoms. Sometimes they are referred to as brown algae, but this is incorrect, brown algae is another type altogether. The algae could also be mistaken as a form of smear algae as the aquarium décor could be covered with a thin layer. Again, smear algae has nothing to do with diatoms.

Diatom algae rely on silicic acid being present in the seawater. If this remains present in any amount it will be extremely difficult to get rid of the diatoms. Tap water could contain the acid in a sufficient amount to support the algae – if it doesn’t it is likely that it will not appear. If there is a sand bed present maybe silicon is present?*

Wandering off-course for a moment, diatoms have a really wonderful cell structure. I have only seen pictures in books. They could be circular, triangular, oval etc and have intricate patterns within the cell that are individual. I don’t know, but I doubt they are singularly unique, but there are many variations. The cells, which are constructed of silicon, don’t degrade and are in fact used in diatomaceous filters. The media is simply made up of these cells.

Anyway, if the aquarist has an invasion of diatom algae then the first thing to do is wait. After a week or two the diatom problem will often die back and cease to exist. The die back usually is not instantaneous but occurs over a period.

If the problem is getting worse, and/or there isn’t any die back, then it is likely that silicic acid is being supplied. I’m not sure of the sand bed bit, but perhaps silicon content within the sand bed is the culprit. If so, then the silicon should exhaust?* Obviously the aquarist should not be tempted to change the sand bed as this could well make matters worse or extend the period when the diatoms are present.

If the aquarist is using tap water then he or she could have the water tested for silicic acid content. If routine seawater changes are being done, as they should be, and the acid is present in the water then fresh supplies are being provided and the diatoms will not go away.

Another way to deal with the tap water is to use reverse osmosis (RO) water. This is tap water that has been filtered through a very fine filter and much of the unwanted content of the water is removed. The purity of the water when leaving a RO filter is generally from 95 to 98%. The use of RO water is recommended whether there is a diatom algae problem or not. RO filters are available to the hobby commercially, are not particularly expensive, and are a good investment.

So, despite the attractive individual cells of diatom algae, the alga is not wanted. Of the nuisance algae types this is probably the easiest to deal with.

(* I have never seen any ‘official’ or science proven reports about the affect of new sand beds in marine aquaria)

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Which Aquarium Salt Should You Use

A long time ago, before I commenced keeping a marine aquarium, seawater had to be mixed by hand using ingredients that had been individually obtained from a chemist. The hobby books of the day, and they were very few, gave details of the mix. This mix was pretty basic, and contained very few trace elements and not many of the minor ones.

As time passed a few dry aquarium salt mixes appeared which had been produced commercially. They did contain most of or perhaps the entire major, minor and trace elements. It was discovered that nitrate and phosphate were unwanted as they had become known as nuisance algae nutrients, and the salt manufacturers made a great show of how their particular salt was free of them.

Now there are many commercial aquarium salt mixes available and they all claim to be ‘the best’. The mixes are now very consistent and considerable advances have been made in trying to emulate nature’s own, the seas and oceans. Some aquarists use natural seawater, and there are anecdotal reports that they have met with success, corals being really well extended and fish healthy. Most aquarists use a dry salt mix however, as it is convenient wherever the aquarist lives.

The production of dry salt mixes has moved on as the hobby has. No longer do marine aquarists struggle to maintain their livestock as technology and knowledge have made it easier. Aquariums that would dazzle those pioneer aquarists of long ago now exist – those where some of the most beautiful fish of the wild reefs are kept, and those where a living captive reef is maintained. Proper husbandry and knowledge plus technology make it possible.

The highest priority for any marine aquarium is the quality of the seawater. This is even ahead of lighting for a reef aquarium, the close second. Low quality seawater leads to problems and there isn’t any need for it. Modern sea salt mixes go a long way to providing this quality. The aquarist needs to be aware of the parameters that are required and maintain them, with supplementary additions if and as needed and routine seawater changes.

So all the aquarist needs to do is go to the local fish shop (LFS) or use the internet and buy what is needed. Basically, yes, that’s it – couldn’t be easier. There are a couple of things to bear in mind though.

The first is that which has already been mentioned. It would be unusual for a dry salt mix to be contaminated with phosphate and nitrate nowadays, but nevertheless the aquarist should be happy that it isn’t. Most manufacturers state the fact on the packaging.

Next the type of fresh water that is being used should be considered. Some aquarists use it straight from the tap, and others use RO (reverse osmosis) water. The latter is where the tap water has been passed through a very fine filter – ‘super-filtered’ it could be called. RO is the one that is recommended as it will have fewer impurities.

If the aquarist uses tap water then what perhaps is ‘ordinary’ salt could be used. This is where the mix contains the ‘standard’ amount of calcium, for example. Tap water contains amounts of calcium (which varies according to location) and there isn’t a need to have additional calcium in the dry mix. If RO water is in use then much of the content of the tap water will have been removed and a salt mix with extra calcium could be used to ensure that the level is brought up correctly. Actually, it shouldn’t be a disaster if either salt mix type is used with either fresh water type, tap or filtered tap, but the salt mixes are there so why not use them.

Then there are the mixes, as above, that claim to be suitable for reef use, as they have extra this and that which usually includes calcium. These find favour with many aquarists.

So choosing a dry aquarium salt mix nowadays is straightforward. There are those mixes that are very well known and have been in use for years, and there are more that could be just as good but are less well known. Perhaps selecting the type that a successful aquarist colleague uses is the best route, or one that is highly recommended on the internet and in hobby magazines.

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Look After Your Membrane

High quality seawater has been said many times to be the number one requisite for success with a marine aquarium of whatever type. It doesn’t matter if the aquarium is fish only or reef, seawater quality counts, though it has to be said it usually counts more with a reef.

The aquarist spends time making sure the seawater quality is high by doing tests for various parameters and carrying out routine seawater changes to reduce pollutants, help replenish trace elements and generally freshen things up.

What about the other end of the operation? When the seawater is made up some aquarists use tap water. Others use reverse osmosis (RO) water, which is tap water that has been passed through an RO filter unit. Using RO water is highly recommended. In this way a large amount of the pollutants that are in tap water – and these vary from area to area – are removed. RO water is generally 95 to 98% pure.

The pollutants are removed by forcing tap water, using mains pressure, through a membrane. This membrane will only permit (nearly) pure water to pass. The rest is allowed to run to waste, unless the aquarist collects it for gardening purposes or whatever. The ratio of purified water to waste water is around 1 to 4 or 5.

The advantage of using an RO filter can be lost. RO filters are pretty simple and require little maintenance but nevertheless occasional attention must be given to ensure efficiency is maintained.

The heart of the RO filter is the membrane. This is where the good is separated from the bad, so it follows that failure here will negate the operation. So protection of the membrane is the order of the day.

There are two types of protection required. The first and probably most important is protection against chlorine. If chlorine has access to the membrane, the membrane will be damaged and will not remain properly functional. Water purity will fall and it is likely that a replacement membrane will be required. (The membrane is the expensive part of the RO filter and it may be worthwhile obtaining a complete new unit.) Protection against chlorine is achieved by using a carbon unit, which is supplied as part of the RO filter. During use there is nothing that needs to be done to the carbon unit. However, when the RO filter is first purchased a note should be made of the manufacturer’s recommendations as to how long the carbon unit will last. This is usually given in gallons and the number will be high. In the home situation the carbon unit will last a long time, so it is worthwhile either logging down the amount of each usage in gallons, or multiplying up the known weekly usage. The aquarist will of course know the amount required for seawater make-ups for routine changes, and also the amount required for evaporation top-ups. The two added together is the weekly usage though it might vary a little. If the manufacturer’s recommendation for gallons is divided by the weekly usage, the answer is the life of the carbon unit in weeks. Once the end of this period is being approached a new carbon unit should be ordered.

The second protection needed is against detritus. There is detritus in tap water though hopefully there isn’t much. Many manufacturers recommend cleaning the detritus filter at intervals of X gallons, and this is all that is normally needed. Looked after, the detritus filter should last the life of the RO unit overall.

Though some more expensive RO filters use more sophisticated methods, an occasional check of the quality of the RO water being produced is worthwhile. A check for nitrate and phosphate is usually sufficient. The test kits should be suitable for fresh water of course.

Maintaining the efficiency of the RO filter helps the aquarist achieve from the start the conditions required for success.

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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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Remember To Test The Output From Your RO Unit

Not more testing! Those aquarists with a reef aquarium will no doubt feel that they do enough already.

The testing here is not of the aquarium seawater, it’s what goes into the aquarium in the form of routine seawater changes and evaporation top-ups. These routine seawater changes are designed to assist in maintaining high quality by replacing at least partially trace elements and ‘freshening’ generally. Taking this into account there doesn’t want to be anything being put into the aquarium that could be detrimental to it.

Some aquarists use tap water and hopefully have tested it to see if there is an excess of nitrate and/or phosphate etc. If there is the advice is to use an RO (reverse osmosis) unit. This device is a filter, where fresh tap water is forced through a semi-permeable membrane. Very nearly only pure water is allowed to pass, the purity of the output is usually 95 to 98%.

The RO unit in action is simple to use and requires very little maintenance. Now and again at the manufacturer’s recommended periods the carbon filter is changed and also the sediment filter though this can sometimes be cleaned. The time span for this maintenance depends on usage but can be very many months.

There are tests that need to be performed on occasion of the output from the RO unit, again not very often. The tests are usually nitrate and phosphate and the check is done on the purified output from the unit. One occasion when the test should be done is when the carbon filter (and to a lesser extent the sediment filter) have not been changed for a while, and the running period is longer than the manufacturer’s recommendation. This is because the carbon filter is there to protect the membrane from chorine. Chlorine can damage the membrane and reduce its efficiency, permitting unwanted substances to pass through it. So it needs to be tested to be sure that it remains fully effective.

Another occasion when these tests need to be done is if the filter has been allowed to dry out. A membrane can be damaged in these circumstances again permitting unwanted contaminants to pass.

If the aquarist does the simple maintenance at the periods recommended by the manufacturer – these periods are often based on gallons of purified water produced – then it is unlikely that there will be a problem. If the membrane becomes less than fully efficient it is often best to purchase a new RO unit, as the membrane makes up the major part of the price.

As with other areas attention to maintenance will maintain peak efficiency.

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Step By Step Seawater Change

Routine seawater changes are recommended for good reasons, for example minimising nitrate, re-introducing trace elements removed by protein skimming and/or activated carbon, and general freshening up.

The guideline for the amount of seawater to change is 10% of the total system net gallonage. This amount can vary once the aquarist has experience of the system, but routine changes should be done.

So, the seawater change and its preparation then. It is assumed that the aquarist has a seawater safe bucket, dry sea salt, scales, tubes for removing and replacing the seawater (tubes with a diameter of around ¾” (circa 19mm) are best), a heater, and an air pump or powerhead. The heater, air pump or powerhead do not need to be powerful, they are not dealing with a large amount of seawater. There is also a need for a hydrometer.

It is also assumed that the aquarist is aware of the amount in gallons that represents 10% of the system net gallonage.

The best fresh water for use in mixing seawater is reverse osmosis (R/O) and the aquarist will need to ensure that there is sufficient for the mixing process.

First, have a look at the instructions on the sea salt package. It is often stated how much salt is required for a particular gallonage at a particular specific gravity (SG) and temperature.

Routine seawater mixes are going to be made many times in the future so on the first occasion a little extra work is required, which will save time on following mixes.

Using the information from the package, pour an amount of salt on to the scales. Keep it below the suggested amount. Note the amount in a notebook (a notebook is a really good thing to have). Now, pour in sufficient fresh water to reach the required gallonage mark on the bucket. Give the mix an initial stir with a wooden spoon or stick.

Place the heater and powerhead (airstone) into the bucket and plug them in. Put the lid on the bucket and run it for around 8 hours or so (do not seal the lid, drill an air hole if necessary), to ensure the salt is mixed and the temperature is the same as that in the aquarium.

After the requisite period has passed, measure the SG of the seawater. Is it low? If so, add a little more salt, but weigh it on the scales first. Note the weight of the salt with the previous note. Continue with this until the SG is as desired, giving plenty of time for the salt to dissolve, two hours or so. When the required result is achieved, add up the total weight of all the salt used. This is the amount you will need on future occasions. Note the total weight down.

If after the initial period the SG is too high, add small amounts of fresh water until it is correct. When a new mix is to be prepared, reduce the amount of salt used and proceed as above, always keeping a note on salt weight for future use. It is unlikely that the SG will be too high – this is why the salt was reduced from the amount recommended by the manufacturer.

Check the seawater temperature is at the level required. If it isn’t, then the thermostat can be adjusted. Remember that SG is affected by temperature, so check the SG after any temperature adjustment.

The SG and temperature should be the same as those of the aquarium seawater.

Once the process to determine the amount of salt needed per mix is concluded, and the heater brings the temperature to the correct level, future mixes are straightforward.

The appropriate amount of seawater in the aquarium needs to be removed. This is easily achieved with a bucket (separate from the new mix bucket) and a hose. The hose needs to be long enough to reach well into the bucket when the other end is at the bottom of the aquarium.

When seawater is being removed it is a good opportunity to siphon out any debris that is seen. To make this easier by better control of the tube, the aquarist can bind the end of the tube to a length of wood which is stiff but not too wide. The wood can be around 12 to 18″ (circa 305mm to 457mm) long, depending on the depth of the aquarium and the aquarist’s needs.

Place the tube with the wood into the aquarium, then give a good suck on the other end and place that end in the bucket. Seawater will flow through the tube into the bucket. A little practice makes the ’suck’ period easy.

If any debris is noticed it is easily removed so long as the seawater is flowing.

Watch the amount of seawater that is removed and when it has reached the relevant mark on the bucket, remove the wood end from the aquarium to stop the flow. This seawater can be discarded.

Putting the new seawater into the aquarium is really easy. If the aquarium is near some stairs, put the new seawater bucket on the stairs and trail a tube down to the aquarium. It may be necessary to have a different tube for this. It is best if someone can ensure that the tube does not come out of the bucket. At the aquarium end, another one of those technical ’sucks’ will start the seawater flow into the aquarium, Once the bucket is empty the flow will of course cease.

If the aquarium is not near stairs, no matter. The aquarist can use a powerhead (use the one in the new mix) and a suitable diameter tube, and pump the seawater in. The powerhead will not remove all of the seawater, the last bit can be put in with a small jug.

All that remains is to check the SG of the aquarium seawater (with the new seawater in) to ensure all is well. If the SG is a little low, just increase the amount of salt a little on the next new seawater mix. Likewise, if it is a little high decrease the amount.

All that remains is to dry the new seawater bucket and store it until the next time, along with its heater and powerhead or air pump.

One note – when removing the heater from a new seawater mix be sure the heater is cool. If it is not and is out of the water, then the glass could crack.

For the first two or three new seawater mixes check that the SG is as desired, and do an occasional check after this. SG checks of the aquarium seawater itself should be done routinely

Routine seawater changes are simple and quite quick if the above suggestions are followed. Anything that simplifies routine maintenance and gives more time for watching the aquarium can’t be bad.

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