Why do fishes keep dying in your tank?

If you are a  person that takes a glass box and you fill it with water and put fish in it; at some point, you are going to end up with a fish that dies. Then you will say to your self: What happened?

Well, the list of reasons why fishes die is very long, but here we have compiled 10 most common causes for fish's death.

Over Feeding

You have heard it a million times but your fish might be doing because of overfeeding. Overfeeding happens for many reasons;

  • One could be that the fishkeeper is a child and they throw way too much food in there.
  • Maybe you are an adult who feels guilty, every time you walk by the tank and the fishes are begging. So, you throw them some food, because you think they are starving.

Overfeeding leads to uneaten food sitting around the tank, contaminating the water as well as excess waste which leads to all kinds of water quality issues.

Give your fish an amount of food that can consume within the first 30 seconds. Don't fall for I am starving act they are gonna give you every single time you pass by the tank.

Your Hands Are Gross

Sometimes it's easy to not pay attention to what you have on your hands when you start doing tank maintenance.

  • Maybe just recently put some really lovely lotion on your hand cause they felt dry.
  • Or you could have just got done going to the bathroom, you washed your hand with soap and you didn't rinse good enough.
  • Or you could have come in from working on your car and you still have a little bit of leftover oil on your hand, that just didn't know.

Our hands are nasty and you got to be careful that you don't contaminate your fish.


It's an unfortunate part of the hobby but it happens; fish kill other fish.

  • Sometimes it will happen right away when you introduce a new fish into the tank.
  • It might happen after they have been together for a while, and one of the fish decided it's time to figure out who the alpha is.

The fact is that aggression is a thing in this hobby. It's is actually up to you; do your research and make sure that the fish you are buying is compatible with the fish that you already have. 

If you are unable to do your research right there on the spot; talk to the employee at the fish store ask them, if this new fish you are buying is okay with your other fish in the tank. Get that out of the way before they bag up the fish to send it home with you.

Believe this, it is no fun to bring a fish home put it in the tank, and watch it instantly get eaten by the other fish. Plus it is just mean. 

Lack of Maintainance

We all are busy and we all get behind on tank maintenance at times; life gets in the way, things happen. But think of it this way;

  • You have got uneaten food
  • You have got waste piling up
  • You have got algae growing all over the place
  • Your water starts to look cloudy, brown
  • Your water starts stinking
  • And your fish are very unhappy

Once it gets to that point, your fish will not last long. 

Equipment Failure

If a piece of equipment fails, it's not always a fishkeeper who is to blame. But it is if something is not done about it right away. It is always good to have a backup plan. This way if something breaks you can react right away and have the least amount of impact on the fish.

You certainly can not have a plan for every possible scenario. But it's a good idea to at least know what you would do. Understand how your filter works, some times if a filter breaks it's only a little impeller that you have to swap out which will just cost you 5-10 buck. And it is super easy, you much rather do that than replacing the entire filter.

Also, another part of the back-up plan would be to have a spare filter sitting around, something like a sponge filter so that if your filter does break, you can put this filter in there and have that running while you take care of your main filter.

It's is also recommended to have an extra heater. If your heater malfunction, you cannot repair it, you have to replace it.

Not Quarantining

Buying a new fish one of the best parts of this hobby and also about being a fish keeper. But sadly, this can also be the time when you ruin everything you have worked so hard for. Unfortunately fish go through so much from the time they leave the fish farm until they reach your tank.

They have to go through so many different changes and they are not always in the best quality water. All of this stress and poor water quality can open up all types of diseases for fish.

You have no idea when you go to the fish store, and you see a fish swimming around, it looks perfectly healthy, but the fish can actually have a disease. Then you take the fish home and you stick it in your tank without quarantining and you get all of your other fish sick.

An easy way to prevent this would be:

  • Take the new fish home put it in a quarantine tank
  • Keep it in there for several weeks
  • Keep an eye on the fish to make sure it's disease-free and it has no problem before you put this fish in with all of the precious fish that you have had for a long time.
  • Some people even medicate their quarantine tank, just to be sure.

Mixing the wrong fish

Some fish would just not go well with others and there are several reasons for that

  • They might require different water parameters
  • Or one fish grows to be 14 inches while the other one only maxes about 2 inches; we know how that ends.
  • The fish that you already have are very peaceful and social while the fish you want is a red devil.

This falls right back to research, know about the fish that you want before you buy them; problem solved.


Fishes do get sick, there can be many reasons why something breaks out in your tank. But you are not sure why you can do everything right and it just still happen. 

Well, basically all this article is about that.

Not Having Lids

Having a lid on the aquarium is a commanding sense, but you would be surprised how many people don't put lids on their aquarium and they end up with fish on their floor.

Some fish are just more apt to jumping than others but there are also other reasons why lids are important. Keeping tank covered helps with evaporation and it also prevents from things falling back into the tank and contaminating the water.

So, definitely put a lid on your tank.


Stress is a killer for us as well as for the fish.

  • Poor water condition
  • Improper diet
  • Lack of maintenance
  • Aggression from other fish

Can all-cause stress among about a hundred other things. Stress is more susceptible to disease. It could stop eating, it could be more aggressive to other fish. 

A happy fish is a healthy fish so, do not stress your fish out.


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