New Tank Syndrome





The addition of an aquarium in your home should be a relaxing and enjoyable experience. Unfortunately, many people find the first four to six weeks frustrating.This tip sheet will help to explain what is happening in your aquarium after you put in your first fish, and what you can do to curb problems that will occur.

Every new aquarium must go through a process called the “nitrogen cycle.” Since the nitrogen cycle only begins when new fish arrive in an aquarium, we call this cycling process, “New Tank Syndrome.” Understanding New Tank Syndrome is important for learning how to keep your fish happy and healthy.

It takes approximately five to seven weeks for the cycle to run through. It is during this time that many fish enthusiasts feel frustrated. Why is my tank cloudy? Why can’t I put in all of the fish I want all at once? Why did some of my fish die?

A key factor in enjoying this relaxing and rewarding hobby is realizing that your aquarium is much like a mini eco-system. In order for your fish and plants to thrive, specific care must be taken, right from the beginning, to ensure a healthy environment.

Before we discuss the steps that your aquarium will go through after adding your first fish, we need to talk about toxic ammonia!


Fish take in oxygen and release carbon dioxide into the water – that’s how they breathe. During this process, a by-product called ammonia is also released. Even more ammonia is released into the water as your fish eat and produce natural bodily wastes. Although these are natural functions, the ammonia is toxic to your fish. It’s understandable that this ammonia problem could be compounded if too many fish are added to the tank in the beginning. More fish = more breathing = more bodily wastes = ammonia build-up! On top of all that, some people tend to over feed their fish. Over feeding contributes greatly to high ammonia levels. Ask your Petland pet counsellor exactly how much food to feed your new fish.

There are many things which contribute to the production of ammonia; however, ammonia is needed, in proper amounts, to begin the cycling process. Since ammonia starts the nitrogen cycle, it stands to reason that fish must be added to start the cycle.

Adding Your First Fish

The type and quantity of fish will depend on the size of aquarium you have and the species of fish you want to keep. The first fish that are added should be hardy.

Once you have added your first fish, they will immediately begin to produce ammonia (as we discussed above). For the first day or two, your fish and aquarium will look normal; however, don’t be surprised if after day two (sometimes up to day four or five) if your aquarium water goes cloudy. This is called “bacterial bloom.” This cloudiness is caused by initial good bacterial growth and is not harmful to your fish. It will clear up on its own. As you will see, you need this bacteria growth for a healthy aquarium. At this point, there is rarely a cause to perform a water change.

Good Bacteria

During the first week that your aquarium is set up with fish, bacteria will begin to grow in the gravel. It will also grow in many other places, such as your filter’s carbon and sponge inserts. This is “good” bacteria, which will consume the toxic ammonia and convert it into a chemical called “nitrite.” It takes a while to grow this good bacteria; usually one to three weeks, at which point it will be abundant enough to handle the ammonia in your tank. Remember, more fish in your aquarium means that more ammonia is being produced, so it is best to add them slowly.

Water Changes

When your tank is going through its cycle, partial water changes done with a gravel vacuum are necessary to help keep the high toxic levels down. Reduce the waste load in your aquarium by performing small water exchanges (25%) once a week for the first five weeks. A Petland pet counsellor will be happy to show you how to use your gravel vacuum. Water conditioners and supplements, such as Nutrafin® Cycle®, should be added after each water change. Once your tank is established (approximately five to seven weeks), a 25% change must be done every three to four weeks to keep your fish happy and healthy. An aquarium operating for six months or longer, will require fewer water changes.


There will be a significant drop in your aquarium’s ammonia level once the bacteria population is hefty; however, your concerns should not be lessened. Remember, that the good bacteria changes ammonia into NITRITE. At this point in the cycle, a second type of bacteria develops, which helps to consume nitrites.


Nitrites converts into a compound called “Nitrates.” Nitrates, unless found in high levels, are generally not toxic to your fish! Unfortunately, this second type of good bacteria is slow in multiplying. It may take up to five weeks for this bacteria to gain control over the nitrites in the water.

Algae Growth

High levels of nitrates act like fertilizer, producing a carpet of algae on the tank floor and walls. You can help prevent this problem by adding live plants to your aquarium. Live plants will help to consume the nitrates, thus reducing algae growth.


Stress from the ammonia and nitrites will undoubtedly have some ill effects on your fish if some preventative measures are not taken. Aquarium test kits should be used to monitor ammonia, nitrites, pH and other water quality conditioners at the beginning and through the life of your aquarium. Your Petland pet counsellor can show you how to test your water. Signs of stress in your fish may include gasping, shaking back and forth, clamped fins or lack of colour. They may also refuse food. Should your fish exhibit any of these signs or are not behaving normally, contact your Petland pet counsellor.