How To Tell If Fish Are Happy In A New Tank

Now that you have gone through all of the steps to set up an aquarium for your fish, you want the fish to enjoy their new environment, too, right? If you decide to keep fish as pets, it only makes sense that you would want to provide them with everything they may want and need to be happy and healthy. While many people may think of fish are emotionless creatures, this couldn’t be further from the truth!

Fish will show you their emotions through specific behavior; with time, you will learn to read them and know whether they are happy, depressed, or anxious. Knowing how to look for this behavior when placing your fish in a new tank becomes even more crucial. We’re sharing the key signs for how to tell if fish are happy in a new tank.

How To Tell If Fish Are Happy In A New Tank – Common Signs

Fish might not wag their tails and stick their tongues out when they’re happy, but when you know what to look for, you will soon realize that fish are cute and quirky creatures with huge personalities! 

Let’s look at the clear-cut signs that your fish are happy in their new tank:

Your Fish Are Happy If They Are Breathing Properly

How to tell if fish are happy in a new tank, may come down to how they are breathing. Fish, like any other living creature, need to breathe oxygen to survive. Signs that your fish are breathing properly include their gills expanding thoroughly and slowly, and then contracting again. 

If you notice these movements consistently, you can rest assured that your fish are healthy and doing well in their new environment. 

Sick or stressed fish will have abnormal breathing movement around their gills, with their gills expanding very quickly and contracting suddenly. 

Changing your water and using a test kit would be best if you notice abnormal breathing. You might be surprised if you see how big of a difference the temperature and water quality can make in your aquarium and your fish!

Your Fish Are Happy If They Are Eating Routinely

Generally, pets will not eat well if they are stressed, depressed, or ill. If your fish are not eating well, it indicates they are not happy. 

It’s essential to have a fixed routine for feeding your fish. It could either be in the morning or at night, and the intervals should be as accurate as possible. This way, it would be much easier to notice sudden changes in your appetite, and you’ll know when something is up. 

However, if your fish seems to ignore their food, the problem may lie with the food you provide. Smelly food, or food with a strong odor, could be off-putting to some fish, as some are picky eaters. 

If you suspect that the type of food may be the problem, you can try to switch up the food. However, if you know your fish is ignoring their favorite types of food, then it is likely that there is a problem with their health, or the health of tank. Check your new tank’s water, composition and temperature to ensure your the tank environment is fish-friendly.

But, if your fish is still eating normally and loving their food in their new tank, this indicates a happy and healthy fish! 

Your Fish Are Happy If They Are Actively Swimming Around

A clear sign that your fish are happy in their new tank is if they are actively exploring and swimming around. Fish that like to explore a new space freely means that it feels safe. 

Additionally, seeing your fish swimming around in the center of the tank is another sign of happiness, as fish that float lifelessly in the water near the bottom or top of the tank are likely stressed or ill. 

Sit down and watch your entire tank, shifting your focus to a new fish every few minutes. A fish hanging out in one place or just lying in a corner indicates they are unhappy. 

However, keep in mind that some fish are just shy, and they may take some time to get used to the new and unfamiliar environment. 

If you notice one of your fish hiding in some decorations or plants, but others seem perfectly happy and healthy, it may just take a while for that fish to become accustomed and happy in their new tank!

How To Tell If Fish Are Happy In A New Tank

Your Fish Are Happy If Their Fins Look Healthy

If a fish has proper and healthy fins in good shape, it allows it to move freely and healthily. If you notice that a fish’s fins are ragged or torn, you can take this as a clear indication of stress or disease. 

Of course, some fish have reputations for bullying other fish and nipping on their fins, but if their fins are severely ragged, you need to separate the fish from the others as soon as possible. 

In the case of a disease, one fish could cause the death of your entire aquarium, which is discouraging for any pet owner.

Your Fish Are Happy If They Are Social And Interacting

When fish are placed in a new tank, some may become aggressive and territorial. 

This is a common problem, as aggression is usually caused by stress, and of course, a new environment could be stressful, especially on more sensitive fish. 

However, every fish has a different personality, and it’s up to you to get to know each of them! Some fish are aggressive in nature, and some are incompatible with being kept in the same aquarium. 

Many aggressive types of fish will defend their territory to death, which could very quickly create chaos in your aquarium. It would be best to research what types of fish will interact with each other to avoid confrontations as much as possible, especially in a new and unfamiliar tank!

A happy fish usually won’t fight with their housemates if you give them ideal water conditions, ample space, and enough food. 

If you notice your fish are swimming around playfully and interacting with each other, this is a clear and positive sign that they are happy and thriving!

Your Fish Are Happy If They Are Bright In Appearance

A brightly-colored fish is a symbol of a happy fish! If you observe that the physical appearance of your fish is pretty and vibrant, you can be sure they are happy. This includes no blemishes or white spots on their body, which means their tank conditions are perfect. 

Usually, when a fish becomes pale with blemishes, it is due to too much nitrogen in its tank water. 

Because fish waste consists mainly of nitrogen, it could cause problems and change your fish’s color. If the nitrogen accumulates in the tank and is not cleaned regularly, it could become dangerous and not only compromise the health of your fish but it could kill them. 

Another sign of a happy fish is when their eyes are not bulging or looks like its popping out of their head. But, this isn’t always true, especially when it comes to some types of goldfish, as this is just how they usually look. 

However, if you notice a healthy glow and standard eye structure on your fish, you can be proud of yourself, as each one of them are happy and enjoying their new environment just fine!

Your Fish Are Happy If They Show Signs Of Breeding

If your fish shows signs of breeding, you can pat yourself on the back. Only the happiest fish will show interest in breeding, which means the conditions of their tank are great, and they are ready to start a family! 

When a male fish wants to mate, he will usually chase the female around for some time until she allows him to get beside her. The male fish will then playfully flick his body against hers, which releases sperm, and she will begin to release her eggs at the exact moment. 

In some cases, a male fish may also wrap his body around the female, and he will then fertilize all the eggs as the female releases them.


Moving your fish to a new tank is likely to take some getting used to. How to tell if fish are happy in a new tank comes down to how well they are breathing, eating, and socializing, as well as their appearance and interest in breeding (if applicable). By looking for these signs of a happy fish, you can rest easy knowing that they’ve adjusted to their new tank.

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