It’s a distressing fact that many fish die at the hands of inexperienced hobbyists (as well as experienced hobbyists who should know better). Often these fish die from what is known as New Tank Syndrome (NTS). In this article I’ll explain what NTS is and how best to avoid it.
Fish, like all living organisms, produce waste; mostly from their gills as a byproduct of their metabolic processes. This waste is mainly ammonia and is poisonous in even small concentrations. In a river or lake the poisons are greatly diluted or washed away and so there is no problem. In a fish tank however the ammonia levels can quickly rise to lethal levels.
In an established mature aquarium there is a population of various types of bacteria. These feed on the ammonia and break it down into less toxic substances. First its converted into nitrite, then into nitrate. Nitrite is still toxic but nitrate is harmless unless at very high levels. The nitrate is removed by regular water changes.
The following diagram shows the process:
The conversion by bacteria of ammonia to nitrite and then to nitrate is part of The Nitrogen Cycle.
The nitrifying bacteria which carry out this process are found on the surfaces in the aquarium – on the gravel, plants and glass. A large population of bacteria is encouraged by providing a biological filter, usually in the form of a sponge, through which water is continually passed. The sponge provides a huge additional surface area on which bacteria can grow and consume the waste produced by the fish.
In a new tank however the number of bacteria is very small and even a modest number of fish will produce more waste than can be processed. The problem is made worse when a large number of fish is introduced into a new tank – ammonia rises to lethal levels within a few days. Symptoms of poisoning by ammonia include:
- Gill irritation – scratching and gasping at the surface
- Skin, eyes and gill damage
- Lethargy, loss of appetite
- Clamped gills, lying on the bottom
In addition fish weakened by ammonia are vulnerable to attack by parasites and various bacterial infections. The addition of “treatment” to the tank at this time, which most shops will be happy to sell, will likely do nothing to alleviate the problem and may even make it worse.
The trick then is to make sure there are enough bacteria in the tank to process all the waste produced by the fish. Although there will be some bacteria even in a very new tank it can take several weeks for the population to grow enough to cope with a tank full of fish. The process of growing a bacterial colony is called “maturing” or more commonly “cycling” a tank.
Traditionally a tank was matured by adding one or two hardy fish and letting the bacteria build up for a few weeks before slowly stocking the tank by adding two or three fish every week. This can still be a reasonable approach provided the tank is big enough and the number and type of fish chosen carefully. There is still a risk to the fish however and the ammonia levels should be monitored carefully – test kits can be purchased at your local fish store. When the ammonia levels increase then water changes should be carried out to reduce its concentration.
A safer method, though perhaps a bit more complicated, is to add a source of ammonia to the tank and let the bacterial colony grow without any fish being present. When the bacterial colony has grown sufficiently fish can be added. This is known as the “fishless cycle” and will be the subject of a future article.
There are a few ways to speed up the process:
- Add plants – healthy plants will consume some of the ammonia and will also have bacteria living on their surfaces. A good growth of plants and especially floating plants can significantly reduce the time taken to mature a tank and will make the environment much safer for your fish.
- Add bacteria – sounds obvious but it isn’t often done. Sources of bacteria are usually some filter media or gravel from an established tank. There are also commercial products which claim to contain nitrifying bacteria.
- Obtain a mature filter – if possible run a filter in a mature aquarium for a few weeks before setting up your new system. When you are ready you can transfer the filter and it’s load of bacteria into your tank.
To summarise – New Tank Syndrome is the condition where a newly set up tank is unable to sustain a healthy collection of fish. It’s caused by the accumulation of toxic fish waste. It can be prevented by ensuring that enough nitrifying bacteria are present to consume all the waste produced by the fish in the tank.