10 Reasons Why Your Fish Die - and Ways to Keep Them Alive

Jen Owens
Face it; the guilt eats away at you. You've brought home yet another molly and another molly swirls carelessly in the toilet going to that big aquarium in the sky. Is it your fault? In my findings... yes, it probably is.

Don't get me wrong, fish die just like the rest of us. Sometimes a fishes days are just numbered, but if you're seeing a trend in the belly-up category, something needs to change.

The following is a an informative measure of common ways that fish end up not so alive, and a how-to guide on what to know and what to look for and how to stop any problems in your fish tank.

Let's now examine the top 10 reasons fish die - and how to prevent them from doing so. These are in no particular order.

Reason number 1: Other Fish

Even if you have a community tank with community fish (those that don't eat other fish), you may find if you watch closely that 1 fish is picking on another fish. Perhaps there are a school of fish that are attacking just for the fun of doing so.

While a community fish devoid of teeth can't literally tear apart another fish, it can do damage and over time, the victim fish will become stressed out, making it vulnerable to disease and bacteria. Watch how your fish interact. Make sure smaller fish have a place to hide and if you see a problem fish in your tank, you may want to put him in a different tank or donate him to a pet store. If you do notice a fish has been attacked you can help that fish recover (after you've removed the offender) by leaving the lights off in the tank a little longer than usual and adding some liquid stress coat to the tank.

Reason number 2: Disease, Bacteria and Parasites

Somewhere along the way your fish may get Ich. Other times, you may introduce a sick fish to your otherwise healthy community. Almost all fish diseases, bacteria and parasites are easily cured with medicines you can acquire at your pet store. Be sure to follow all instructions carefully, as some require removal of your activated carbon and treat until you are instructed to stop. Overmedicating is never a good idea, either, so examine your fish closely while they're healthy. Knowing what your fish are supposed to look like will aid greatly in the event that they become ill.

Reason number 3: Stress

There are a number of factors that can be held responsible when it comes to stress in an aquarium environment. Almost everything can put stress on a fish. Stress is a vicious circle in fish, same as it is in human beings. The more stress they experience, they less prone they are to being able to fight off disease, other fish, unfavorable water conditions and more. Stress is more a catalyst within other causes than a cause itself, but on the flip side of that it is always a major player in unhealthy fish.

Reason number 4: Overcrowding

This may seem obvious, but just because your fish look like they've got enough room to swim about doesn't mean they actually do. While fish don't physically like to be crowded, it's more than that. Ammonia levels can rise if there are too many fish in a tank, and ammonia is deadly to fish. A good rule of thumb to use when it comes to stocking freshwater tropical fish is an inch of fish per gallon of water. This means only 10 small fish in a 10-gallon tank. Don't try to get away with too many fish in a tank even if you have really good filtration. Water test kits are available for purchase at pet stores or you can usually take a water sample up to a pet store and they will test the water for you.

Reason number 5: Overfeeding

This is usually only a fish killer it taken to an extreme, but is still dangerous even in a small capacity. Feed both according to your fish food instructions and pay attention to how much food your fish actually eat as opposed to how much you are feeding them. Uneaten food will collect at the bottom of your tank and from there decompose, sending ammonia levels up higher than they should go. Investing in a small catfish will help keep uneaten food down to a minimum... and hey... they even spice up the tank!

Reason number 6: Improper Mechanical Filtration

You need more than an air pump and some airline tubing to keep the water in your aquarium healthy. Power filters are marvelous for this. You want to acquire a power filter that will cycle your entire tank, in gallons, 3 to 5 times an hour. Change the filter inside your power filter once a month. After that time, the floss is dirty and the activated carbon is no longer effective.

Reason number 7: Improper Chemical Filtration

Generally, once a tank is established you can lay off the dechlorinator and stress coat. However, anytime you perform a partial water change, both stress coat and dechlorinator is important. Same when adding new fish to your aquarium. A little stress coat will make everyone involved feel a little better.

Reason number 8: Improper Temperature

A tank heater is really essential to your tank. A few degrees in either direction doesn't effect us as much as it will effect your freshwater tropical fish. You want to keep your tank temperature as stable as possible. Check to make sure your heater is functional every so often. There is an assortment of tank thermometers available for under $5. Too hot or too cold temperatures, and especially changes in temperature can have a very negative effect on fish. Remember, the smaller the tank, the more vulnerable it is to temperature variances.

Reason number 9: Dirty Water

If you do a partial water change (about 20%) once a month, you should be ok. Change your filter at this time, remove algae from the tank and when you refill, be sure to add dechlorinator and stress coat. If it's been way longer than a month, or you just "top off" the tank when it gets low, you're not removing any ammonia or nitrates. These do not "evaporate" with the water, but rather stay in the existing water. Levels increase while healthy water decreases.

Reason number 10: How You Treat The Fish To Begin With

If you go to a store and get a new fish, do it after your daily errands. Don't lug a fish around all day long in that little plastic bag. There is a limited amount of oxygen in that bag. There is no place for your fish to go. It is stressful to be in that plastic bag for a long time.

Instead, buy the fish, take it home and float the bag in your aquarium for 15 minutes. Afterwards, open the bag and dump the fish and the water from the bag into a fish net. Don't just pour the water in the bag into your aquarium. Place the fish in your tank and enjoy. Keep the stress to begin with low and you'll have a much greater chance at your new fish being healthy and adjusting easily.

Basically, know your fish and use common sense. If you're going to keep fish, set them up an aquarium environment that promotes their health. Thriving fish are not only a source of pride but also a relaxing component to any room in your home.

Published by Jen Owens

Twenty-something, opinionated humorist with just a bit of cynicism. Yes, just a bit.  View profile

  • Knowing your fish will help diagnose problems before they become life or death issues.
Stress is a catalyst in any situation that can be detrimental to the health of your fish.

44 Comments

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  • Sue Judith Gartman3/17/2011

    An aid who comes and helps me went to the pet shop today and purchased one small catfish and three small community fish. The catfish and two of the community fish have died already. I had two gerammi fish in the tank. They are fine. Just one little fish is left. I called the pet shop and the worker that answered the phone told me that sometimes fish can be stressed when they are transported from one fish tank to another. The change in environment can kill them. He thinks that is what happened to my fish.
    Please advise. I will get fish to replace the ones I lost. Very unhappy at this point.

  • finia1/17/2011

    i have a goldfish in a glass bowl and have to clean its tank everyday. WHY
    and when i try to net it out using a cup it swims away

    can someone answer my question please

  • gust 31/17/2011

    I just bought 3 goldfish at the start of the year. Their still alive.
    Maybe you just aren't taking care of them properly.

  • gar1/16/2011

    I got 4 new white cloud mountain minnows, and after about 10 days the grey one died(3 gold and 1 grey), he seemed to not eat while all of the gold ones did. I know that they were the same type because they were in the same tank at the pet store. Can anyone respond to me with ansewers before the others die?

  • mee1/4/2011

    omg i just bought a fish on sunday one died on monday the other one died this morning i want to know why if i fed them right?

  • Ethan12/29/2010

    why do all my damn fish keep dying

  • John12/14/2010

    Mrs. ninia
    Since you moved the goldfish to a different spot that might be the problem. The goldfish and betta fish are not the same so what ever you do don't put it where the betta fish is.

  • John12/14/2010

    Another thing if you're fish do not eat their mouth might have been hurt by the rocks, and gravel, or other fishes might have bited it.

  • John12/14/2010

    Well if you're fish dies what ever you do bury it. Fishes are like humans, you don't flush your dead grandparents after they die I mean that's insane. And they're are good fertilzer for you're garden.

  • john12/4/2010

    well folks it's either that you have the wrong fish food, make sure the temperature in the water is warm, and always ask a helper to make sure you get every information about the fish and what they need, what kind of water, and always the food.

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