Betta Fish New Tank Syndrome

You’ve got your community tank up and running for about a week. Or, perhaps you just have one male betta in a tank over 5 gallons large. Suddenly, the water gets cloudy, and the fish are either dead or gasping for air at the water’s surface. Your aquarium is suffering from new tank syndrome.

What is New Tank Syndrome?

New tank syndrome happens when there are not enough beneficial bacteria in your tank to convert chemicals that kill your fish, ammonia, and nitrite, into nitrate, a less harmful chemical. It can happen to older tanks too, if changes are made too abruptly.

It takes time to build up a colony of beneficial bacteria large enough to handle the poop and uneaten food that fish create. Only beneficial bacteria can do this. Your tank’s filter cannot. Filters are still needed for other reasons, but even the most powerful filter cannot prevent new tank syndrome.

This is because of a complicated chain of chemical reactions that need to take place in your tank called the nitrogen cycle

The Nitrogen Cycle

Fish produce waste from their poop and from all of the food that they do not eat. All of this decays, forming ammonia. Too much ammonia can kill your fish.

Beneficial bacteria on the surfaces of your aquarium eat the ammonia and convert it to nitrite. Too much nitrite can also kill your fish.

But, wait – along with the beneficial bacteria that eat ammonia are bacteria that eat nitrites. They then convert nitrite into nitrate. Too much nitrates can also kill your fish, but regular water changes easily take care of that.

Anyway, it takes time for ammonia to become nitrate, through the two kinds of beneficial bacteria. It takes about a month, but can take six weeks or more. 

Can’t You Just Set the Tank Up and Wait a Month?

There are many places online that recommend just setting the tank up, filter, heater, air stone and all, and letting it bubble away for a month, then the tank will be magically ready to add fish. I’m guilty of giving this advice myself years and years ago.

Looking back now, I see that any tanks that worked out despite me not cycling (or even testing the water) did so because I just happened to be lucky. The times that I was not lucky I assumed that the fish were sickly or that I overfed them or the equipment failed or something else.

You can set everything up and wait a month, provided you add a source of ammonia to the tank. The least expensive way is by adding fish food to the tank. 

You need to keep testing the water to see if ammonia and nitrite nearly disappear or is, at the most, 0.02 ppm. At first, your tank won’t have any nitrates at all. You’ll know when your tank has cycled when the nitrate levels reach below, but not over, 25 ppm.

Speeding Up the Nitrogen Cycle

There are some ways to speed up the nitrogen cycle:

  • Get a cup full of gravel from a healthy tank and add it to yours.
  • Add commercially available beneficial bacteria. However, this only works if there is a source of ammonia in the tank. You can do this by adding a little fish food every day. When it rots, it creates the ammonia that the beneficial bacteria need to eat.
  • There is also commercially available bottled ammonium chloride made for just this use in aquariums, which you add before adding the beneficial bacteria. You’re going to need space for a lot of little bottles if you use this method.

In the old days, fish keepers would use a sacrifice fish, usually a guppy, which usually died. Its dead body would create enough ammonia to get the cycle going. I do not recommend this method, as it’s cruel. I mention this because I still see this method recommended in many places online.

I’ve also read of people urinating in their fish tanks to get the cycle started. I’m hoping that those people were kidding. Please do not pee in your betta’s tank.

Can New Tank Syndrome Happen Without Causing Cloudy Water?

Yes. New tank syndrome can happen without causing cloudy water. Ammonia and nitrite levels can spike so quickly that your fish are killed off overnight or you find them gasping at the surface. 

Other signs of ammonia poisoning in fish are that their gills turn red or deep purple and they lose their appetites. Soon, their fins clamp to their sides and they may sink to the bottom of the tank and die, or float to the top and die. Either way, the fish die, unless quick action is taken.

Causes of New Tank Syndrome in Older Tanks

Sudden changes in old tanks can cause new tank syndrome, such as:

  • Too thorough of a cleaning, which winds up killing the beneficial bacteria.
  • Overfeeding your fish.
  • Putting too many fish in your tank.
  • Complete change of gravel or substrate. Keep a cup or so of the old substrate in the tank at all times.
  • The temperature suddenly went up or down. 

Saving Your Fish

The best way to save your betta or any other fish that are still alive is to do a partial water change. Do not do a 100% water change, as this will be too much of a shock to the fish, and they’ve been shocked enough, already.

Also, do not clean the walls, the decorations, the gravel or change the filter media. Just change some of the water. The beneficial bacteria live on surfaces, including everything you may be tempted to clean. Even leave fish poop in there so the beneficial bacteria have ammonia and nitrite to feed on.

If you have a hospital tank, place your betta in there and keep him or her there until the old tank cycles. Keep testing the water to see if the ammonia and nitrite levels are down and the nitrate levels go up.

Does New Tank Syndrome Happen in Aquariums Less than 2 Gallons?

New tank syndrome rarely happens in very small tanks only when the water is changed often. In this way, it’s changed before toxic levels of bad chemicals build up. 

Does this mean that bettas should spend their whole lives in tiny aquariums? Absolutely not. Although one- or two-gallon tanks are great for hospital tanks, or to place a betta temporarily before moving into another tank, they are not good for bettas in the long term.

The Least You Need to Know

New tank syndrome is when the water gets really cloudy and your betta is gasping for air at the water surface. This happened because the tank was not cycled properly. For now, do partial water changes, making sure to clean nothing else, to save the betta and any other fish in the tank. If you ever start a new tank, make sure to take the time to cycle it properly. Only add one or two fish at a time to a community tank to avoid ammonia spikes. Never add fish the same day as setting up a new tank.

You can read more on how to acclimate your fish here.

About the author

Hi, I am Rena.
I grew up in a house surrounded by fish tanks.
I have spent my life caring for and writing about fish.
I have studied journalism and worked for online and print magazines.

You can find the articles I wrote here

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