7. A guide to water chemistry - Maintenance

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7. A guide to water chemistry - Maintenance

Postby Andrew W » Fri Mar 12, 2010 9:38 pm

So far we have dealt with the hardness, softness and pH of your water, what these terms mean in relation to keeping fish and how to make adjustments or modifications to the water in accordance with the needs of your fish. This however is not the sum of all you need to know. It is one thing to create water of the correct chemistry for your fish; it is another thing entirely keeping it that way.

An aquarium is an enclosed environment and so nature plays no part in its maintenance,that is entirely down to you, the aquarist. There is a biological cycle at work in your aquarium and if it is not monitored it can have a devastating effect on your fish.

All aquaria contain organic mater such as waste, uneaten food, rotting leaf matter and also (but hopefully not) overlooked dead fish. The biological breakdown of these products and the fish themselves produce ammonium, this is not in itself toxic to fish but in an aquarium with a pH greater than about 7.0 ammonium can be converted into free ammonia, which is very toxic to fish. This is a problem that is normally associated with newly setup aquaria. The reason for this is that as a tank matures it will have established a population of the bacterium Nitrosomonas spp., these bacteria convert the ammonium and ammonia to nitrite. A useful way of lessening the build up of ammonia and ammonium in a new aquarium is to seed it with media from an established aquarium.

This can be done by using substrate, water or filter media from the mature tank. Nitrite is also toxic to fish although not to the same degree as ammonia. As well as the Nitrosomas spp. bacterial population in your tank there is another population of bacteria identified as Nitrobacter spp., this second population of bacteria converts nitrite to nitrate, which is only toxic in high levels. Nitrate is removed by carrying out regular water changes. This is a continous biological process with the conversion of ammonia and ammonium into nitrite and then into nitrate.


In a mature healthy tank the bacterial populations will be working continously with the effect that there should be virtually no ammonium, ammonia or nitrite in your aquarium. It is very important that regular checks are carried out on your water to ensure the continued absence (or at the least very low levels) of these pollutants. Ideally nitrate levels should be maintained below ~25ppm.

In the event that you experience high levels of ammonium, ammonia, nitrite or nitrate (as previously mentioned, this is usually associated with newly setup aquaria) they must be removed as soon as possible or your fish will start to suffer. There are two methods commonly used to achieve this;

> The first is to do a 50% water change immediately then a minimum of a 10% water change daily until the levels are down within tolerable limits. The drawbacks to this method are that it can be messy and time consuming, it can also stress the fish quite considerably and also removes a lot of the beneficial bacteria needed to neutralise the toxic chemicals, this is especially important in new aquaria where the levels of bacteria have not had time to build up.

> The second method (and one the author found to be very effective) is the use of ion exchange resins. As mentioned in the section concerning soft water, ion exchange resins are available that can target and remove a specific ion, such as ammonium, ammonia, nitrite or nitrate. The resins for this particular task are readily available and most often come in a puch containing the required resin beads. The pouch is placed in the water, preferably within the filter so that it receives the maximum flow of water over and through the pouch. The main drawback is that the toxic ions are replaced with non toxic ions, usually Sodium ions. However the benefits outweigh this consideration and based on experience the resins work very fast giving a considerable reduction in toxins within 24 hours. They are also a lot less time consuming and less disruptive to the fish that will already be stressed from the effects of the exposure to the toxins in the first place.

As mentioned at the beginning of this section an aquarum is an enclosed environment with relative limitations; everything that happens in your aquarium is proportional to its size and the volume of water it holds. Any problem in a small tank can quickly escalate into a big problem, whereas any problem in a large aquarium will not only have a small initial effect, it will allow you time to deal with the situation. It is very important to know the limits of your own aquaria and not to exceed them. As an example; if you overstock your tank, no matter how clean your water starts off the biological process of nitrification will be unable to deal with the rapid build up of toxins produced by the fish (ammonia/ammonium). Consequently you could end up with an aquarium filled with dead fish.

Knowing your aquarium limits means:-

> DO NOT over stock

> DO NOT over feed

> DO NOT leave rotting matter in the tank (uneaten food, leaves, etc)

> DO make regular water changes (recommend as a minimum 20 to 25% per week)

> DO maintain your filters in good condition

> DO check your water regularly (weekly) for pH, hardness (GH & KH) and nitrate (for new aquaria also include ammonia and nitrite tests).

It is important to remember that when doing water changes with tap water it should be pre-treated with a water conditioner. Water companies use Chlorine and Chloramines to disinfect water supplies, tap water may also contain variable levels of heavy metals. All of these are harmful towards your fish and should be removed prior to use. A number of water conditioners are available commercially that are effective at removing the contaminants identified above.

One of the points made above concerns keeping your filters in good condition. This means not allowing them to get too clogged with waste matter. This is achieved through periodic cleaning of the filter sponges, however it is important to remeber that these sponges contain the greatest concentration of essential bacteria. The best way to avoid clogged filters and maintain a healthy population of bacteria is to cut or divide the filter sponges into two halves, whilst carrying out water changes clean one half of the sponge in the tank water taken out during the water change. Never clean sponges under a running tap as this will remove the essential bacteria. By alternating the cleaning of the two halves of the sponge the filter os prevented from clogging whilst retaining a healthy population of bacteria.

In conclusion, a careful, structured regime of weekly water checks coupled with a water change and any other maintenance as needed will ensure that yor fish are kept on the best of health for many years. It's not hard work and as an aquarist that is your commitement to your fish.

Some aquarists will tell you that fish keeping is actually the art of keeping water, if you get that right the anything is possible. The dream of many aquarists is to sucessfully breed their fish, here, a pair of Pterophyllum leopoldi with the newly free-swimming fry. Photo by A Wood.
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Andrew W

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Re: 7. A guide to water chemistry - Maintenance

Postby blackghost » Sat Mar 13, 2010 1:28 am

I would argue a couple of points here.

Firstly, removing water does not remove bacteria in any number, as bacteria are 'stuck' to filter media (and in fact all non-living surfaces in a tank) and are in the water only in negligible amounts. The exception to this is 'cloudy water' which is common when cycling new tanks, as the presence of large amounts of ammonia produce a population explosion of bacteria - so many that they cloud the water before they have had the chance to find the filter media and stick to it.

Secondly, filter bacteria are very difficult to dislodge from filter media (if they weren't, fluidised sand filters would be impossible). They produce a type of adhesive that sticks them to it, so the whole filter media can be vigorously rinsed in tank water at the same time, with no ill effects. Tapwater doesnt dislodge the bacteria, it kills them because of the chlorine/chloramine present.

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