Sick Fish

A sick fish in your tank is usually an indication of four things: the quality of your water, the temperature of the water, stocking problems, and environmental stress. So, if you have a sick fish, the reason could be any of the four mentioned.

That said, you can easily avoid having a sick fish in your tank by making sure the quality of your water is ideal, the water temperature is consistent, you do not overstock, and you do not put your fish under too much stress.

Sick Fish



– Poor water quality. Constantly monitor the chemical parameters of your tank. Change the water regularly (at least once per week) and watch out for ammonia, nitrite, nitrate, and the pH levels of your water. Remember that you must recreate their natural living environment as much as you could.

– Water temperature. More than keeping the temperature of your tank ideal, strive to make the temperature consistent. Sudden temperature changes can stress fish and make them sick. The ideal temperature for a freshwater aquarium is between 65 degrees Fahrenheit to 80 degrees Fahrenheit. On the other hand, for a saltwater aquarium, the temperature should be between 55 degrees Fahrenheit to 80 degrees Fahrenheit.


– Stocks. Do not overstock. The ideal ratio of fish to the size of your tank is 1:1. For goldfish, add 10 gallons for every additional goldfish. This is because goldfish can grow up to 26 inches. For a fish to be healthy and happy, it needs a lot of room to swim in.

– Stress. Stress can come from anything, such as from when you ship it or when you’re cleaning the aquarium (if you’re netting them too much). It could also come from bullying from other fish in your tank and from environmental conditions they’re living in, such as those mentioned above. However, stress often leads to diseases because the immune system of fish at this time is low. Experts claim that fish get stressed more often before they get sick than get stressed because they got sick.

It is important to note that bacteria and viruses (pathogens) are always present in your fish tank, just as it’s always present in the human environment. No matter how much you keep your aquarium clean, bacteria will grow. Weirdly, an over-clean aquarium is not good either. Fish need beneficial bacteria to survive. The key, then, is controlling pathogens in your aquarium by sticking to ideal chemical parameters.

Finally, remember that being in an enclosed container, such as a fish tank, your fish are helpless and are entirely dependent on you for everything. For example, they can’t just move away to colder water if the heat is too much in your tank or if the ammonia is too much for them to handle, just as they don’t have many places to hide in if fish are bullying them. So the health and the life of your fish depend on you in every way.