I have seen many posts on different forums and Facebook groups concerning new keepers and fish dying. It almost seems to be that new keepers are over anxious to stock their shiny new tanks with fish, which is understandable. This is where the problems begin, as many local fish stores (lfs) do not take the time to explain the cycle to purchasers, instead concentrating on taking in the money. A lot of lfs will sell tanks and fish on the same day, a recipe for disaster. So what is the cycle and what is new tank syndrome?

In its basic form, new tank syndrome is causing your fish to suffer ammonia poisoning and die. Why does this happen and what can you do to prevent it? I make no apologies for the “Noddy” explanation that follows.

You nice shiny tank, equipment and sand are all basically sterile. Although bacteria exist on every surface we touch, they are of the wrong sort and not enough in quantity to process the waste that your livestock will produce. As humans we are lucky to have a sewerage system which allows out bodily waste to be flushed away and dealt with by someone else. Fish in an enclosed environment on the other hand, do not have this facility and have to live in their own waste. So what can we do to overcome this problem?

In a freshwater system you will probably have a filter of some sort, either internal or an external canister. In a saltwater environment, you may also have a filter, but possibly live rock too, which is a filter in its own right. Lets deal with the basics first.

If you have a new filter, you will need to mature it before adding fish to the system. How is this done? You can purchase expensive bio filter “starters”, you can use a cup of sand from an existing system or you can do it from scratch. Whichever you choose, you will then fill your system, set the filters running and bring up to temperature and have your test kits, you are now ready to start the “cycle”. This is the conversion of toxic waste products into less harmful products.

To begin the cycle (I will deal with live rock later) you will need to add a food source to the system. Some people put a prawn in, some people use pure ammonia and some just use fish food, this is known as the fishless cycle. Please don’t use cheap fish to do this, it isn’t really ethical these days. Once your food source begins to rot, it will produce ammonia. Ammonia is extremely toxic to all life in an enclosed system. The good news is that there are bacteria which will feed on ammonia. These bacteria will multiply quickly to a point where ammonia is reduced to nitrite. Nitrite is also poisonous to aquarium life in high levels (above 0.1ppm in a saltwater aquarium and ideally should be 0). Once nitrite is visible on your test kit you know the cycle is underway, different bacteria will now grow to process this product into the less toxic nitrate. Nitrate should ideally be below 10ppm for a system with corals in, up to 50ppm is acceptable for fish only systems or freshwater. With sponge/ canister filtration, this is where the cycle ends. Your nitrates will continue increasing unless you dilute it with a water change and water with a lower nitrate content to that in the system. Keep adding small amounts of food or whatever you used to start the process and make sure it is immediately processed by the filter, only at this time can you consider adding fish.

If you have live rock that has been out of the water for a while, you will experience “die off” on the extremities. Once the rock is in your system the die off will be your ammonia source. Bacteria is already living within live rock, so you have have an almost ready made filter. There will still be an ammonia spike, there will also still be nitirite before you then see nitrate readings. The tank should be “fed” again a few times to ensure the bacteria is sufficiently colonised.

Once you are seeing no ammonia and (preferably) 0 nitrite on your test kits, it is safe to start adding livestock. However, do not go mad at this stage and fill to capacity. Each time you add a fish to the system, the bacteria have to catch up. If you buy 3 or 4 fish, don’t feed them for a day or two so they are not producing excessive amounts of waste. After a couple of days, start feeding sparingly and your bacteria will soon be up to correct levels, you can then add more, feeding sparingly each time. The big problem here is that once new owners see correct levels, they go out and buy multiple fish and (over)feed them. What happens now is that the fish will excrete ammonia which there is not enough bacteria to process. Ammonia levels will rise quickly and the fish will suffer and potentially die. This is new tank syndrome. This is what frustrates new owners the most and puts of untold numbers of potential fishkeepers off the hobby.

Hopefully this is a basic guide of what new tank syndrome is and how to avoid it. Happy fishkeeping.