How to Tell if Fish are Happy in New Tank

Swimming Normally

If your fish is swimming around normally in your aquarium, it is a sign of happy fish. But if the fish is staying in one corner of the tank and not moving around much then it is a sign that they are not happy. 

There are a number of reasons that could be the cause. Poor water conditions might be one reason that they’re not more active. If the pH, water temperature and toxic compounds are off the fish will be stressed and not feel good. They will stay in one corner and not interact with other fish. Healthy fish will swim around normally inside the aquarium, not be stationary or darting quickly.

When introducing fish to a new tank they may sometimes hide behind plants and decorations. This is normal in the beginning and they should generally come out and swim. 

 Breathing Properly

Fish expanding their gills normally is a sign of happy fish. Irregular breathing patterns like labored breathing can be a sign of unhealthy or unhappy fish. High levels of toxic compounds can cause them to breathe irregularly, as if it was hard for them to breathe. If your fish is breathing irregularly, perform water tests to identify what the cause is. Once you know, you can do what you need to do to improve the quality of the water.

Eating Normally

Generally pets don’t like to eat when they are sick or not happy. If your fish are not eating normally it could mean they are not happy. This can be caused by food that’s not appealing or some are being bullied by another fish, or a build up of toxic chemicals. 

Some fish are picky eaters and they may not eat much if it’s not their favorite food. Changing the food you give them may help. If you change to their favorite food and your fish still refuse to eat there may be health issues that need to be addressed. 

One important thing to remember is that some fish are bottom feeders. They will go to the bottom of the tank to eat food and may not show excitement like other fish when they are fed.

Fins Look Good

Fish who have all their fins and are in good health are usually happy. Torn or damaged fins are a common problem in fish that causes swimming problems. If your fish cannot swim properly it can cause unwanted stress. Damaged fins are usually caused by a health issue like fin rot disease and should be treated immediately. 

If your fish have all their fins in good condition and they are able to swim normally, then they are probably happy. 

Vibrant Colors

If the color is dulling on your fish it is an indication of a health problem. High levels of nitrogen can cause their color to dull or fade and make the fish feel stressed. Water conditions should be checked immediately to find out if high nitrogen levels are the cause.

If their colors are vibrant then you know your fish are not suffering from high nitrogen levels. Good water conditions and not over feeding them will keep your fish in great condition. Keeping their colors nice and vibrant not only keeps them healthy, but makes your aquarium look better, and should keep you happy. 


If your fish interact with other fish normally in your aquarium then they are happy. If your fish are fearful of other fish in the aquarium, they will hide in one corner and will not interact normally. Keeping the aggressive fish in a separate tank, getting a bigger tank, or creating hiding spots should improve the quality of life for your fish. 

A happy fish will love to swim around in their groups and play with other fish. They will not fight or get aggressive with others. Sometimes the fish may respond to you when you get close to the aquarium, to feed them or look at them. 

That said, different fish have different temperaments. While many are social, some may interact less with others in a community tank. It’s best to observe them and see if they show any other signs of a problem before determining your fish is not being social.