These fish do not display signs of stress in the same manner as other animal but that does not mean that they do not experience it. When they experience distress their immune systems are compromised, they may change colour, and they will generally lack energy. There are a few things you can try if you think your fish is suffering from anxiety.
The easiest thing you can do to support your fish when they are experiencing stress is to change the water regularly. This will ensure that all of the levels of ammonia and nitrates will remain regulated. It also helps to remove toxins from the water that contribute to the negative impacts of distress. The temperature of the water also needs to remain regulated to help your fish stay happy and healthy.
Some of your fish may be suffering from anxiety due to other fish who are bullying them. If you notice any of the inhabitants in your tank acting aggressively it is a good idea to remove them from the environment. You may notice a significant improvement in the overall happiness of your fish. It is also incredibly important that the fish in your tank have enough room to grow and thrive. Not having enough space is one of the most common reasons that these fish become aggressive or distressed.
Another common reason these fish become anxious and suffer health issues is that they have not been introduced to their environment appropriately. To help your new shoal member get used to their new home there are a few things you should do. When you get home submerge them in the water still in the bag that you brought them home in. Leave them there for a few hours before releasing them into the water. This will help them get used to the water while also giving the other inhabitants the time to get accustomed to the new member.
Other things you can do to avoid distress in your tank is to make sure that your fish are well fed, there is enough room for everyone, and that you only keep species that are compatible with one another. It is also important for your tank to have good oxygenation levels and a proper filtration system.
Distress in your tank is something that cannot be avoided at all times. However, with some basic management techniques, you can reduce this phenomenon significantly.