How to Prevent New Tank Syndrome

Once you have established a maintenance routine, caring for your fish can be fairly straightforward. In the first few weeks after you have introduced the fish, however, the new aquarium will require more attention, primarily to prevent the risk of deaths from new tank syndrome. This problem arises when the fish produce more waste than the new bacteria in the filter system can break down.

Testing for ammonia

If there is a build-up of ammonia in the water, from waste that has not been effectively broken down, this is toxic to the fish. Effects may include damage to the lining of the intestinal tract, interference with the correct functioning of the nervous system, and harm to the gills. You can buy a test kit to check the ammonia level, but the results need to be considered in relation to the water’s pH. In an alkaline aquarium, the effect of ammonia is significantly greater due to a chemical reaction, so tropical fish in these conditions are therefore most vulnerable to new tank syndrome. Temperature also has an effect, with toxic levels of free ammonia rising more rapidly at higher temperatures.


Some of the tank’s beneficial bacteria are Nitrosomonas bacteria, which use oxygen to convert harmful free ammonia to nitrite (NOz). While nitrite is in general far less toxic than ammonia, some fish are still very susceptible to it in high levels. For example, discus (Symphysodon discus) are vulnerable at a nitrite reading of just 0.5mg/litre, although many tropical fish are unaffected until the concentration is 10-20mg/litre. Effects of nitrite are most pronounced in soft water.

Nitrite poisoning affects the fish in a highly specific way: it acts on the red blood cells, modifying the haemoglobin which carries oxygen around the body, preventing this reaction from taking place. Fish suffering from nitrite toxicity have gills that are brown rather than reddish as a result.


The production of nitrate occurs due to the action of different bacteria – the Nitrobacter species. Nitrate is not generally a problem as far as freshwater tropical fish are concerned, although fry are more susceptible to a buildĀ­up than adult fish. Two exceptions are discus and fish living in brackish water, neither of which will thrive in high nitrate conditions. The simplest way to combat the problem is to carry out regular partial water changes. This is especially important at first, until the filter systems are fully functional.

It is not just the fish’s waste that can influence the levels of nitrate. Uneaten food has the same effect, which is partly why fish should not be fed more than they will consume within a few minutes.

Partial water changes

It is vital for the health of the fish that you change a proportion of the water in the tank on a regular basis, partly because it helps to prevent a build-up of nitrate in the water. It is usually recommended to change up to one-quarter of the water every two weeks, particularly in the first months after setting up the tank. Replace it with water that has been treated with a conditioner and is at the same temperature as that within the aquarium. The easiest way to carry out a partial water change is to use an aquarium siphon, which simply transfers water to a bucket placed on the floor.

Safe siphoning

When siphoning out the water, never, ever start the flow through the tube by sucking the lower end, or you could end up seriously ill. Instead, fill the tubing with conditioned water, using a watering can with a narrow spout, and place a thumb over each end. Then put one end in the aquarium, removing your thumb here only once the end is below the water level, and taking care to prevent the tube from lifting out of the water.

Once the other end of the tube is safely in the bucket, release the pressure of your other thumb, and the water should then flow into the bucket. When the right amount of water has been siphoned off and you want to stop the flow, place your thumb back over the lower end, lift the tube up into the aquarium so that the water can drain out, and then remove it.

Battery siphons and gravel cleaners

You can also buy battery-operated siphons, but the flow is sometimes less predictable, particularly if gravel becomes accidentally sucked into the machine, which may prove hard to dislodge. A useful additional piece of equipment which may be operated in conjunction with the siphon is a gravel cleaner. This helps to prevent the filter bed from becoming stagnant, with a resulting decline in numbers of beneficial bacteria. It stirs up the gravel and removes the mulm (decaying organic matter), without sucking up the substrate medium. A plastic cup at the base keeps disturbance within the aquarium to a minimum, so that plants will not be uprooted.

Filed Under: Pets & Animals


About the Author: Fred Goodson has a passion for pets and animals. He has 4 dogs and is planning to have another one. He is also a blogger who writes about pets and animals. Currently, he is living in New Jersey.

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