Unfortunately, a part of being an aquarium owner is facing the inevitable. Dead fish are bound to pop up throughout time.
A fish should be removed from the tank immediately after death. Of course, you may notice the incident right away but it is important to remove the fish as soon as it is noticed. This is because a fish will start to decompose right away and will release harmful toxins into the tank.
Read on to learn more about what exactly happens to your tank when a fish dies and what steps you should take.
Remove the Fish and Test Ammonia Levels
The first step to take when you find a dead fish is to remove the fish right away. Make sure to use a net instead of your hands as you do not know how the fish has died.
If you can not find the fish, try looking into where it may be hidden, or the fish may have already been eaten by another tank mate.
It is also possible the fish may have jumped out of the tank entirely and may be on the floor nearby. Also, check inside your filter as a more powerful filter system may suck up the fish entirely.
After removing the dead fish from the tank you should test the waters for ammonia levels. Depending on the size of the tank determines how fast the water can become polluted from a dead fish.
For example, a smaller tank will become polluted quicker than a larger tank. Meaning in a 5-gallon tank the water will become polluted almost immediately.
Whereas a 30-gallon tank may take days to become polluted.
It is important to check your ammonia levels as a dead body will affect those levels. As the beneficial bacteria typically take care of ammonia in the tank water, a dead body gives off so much ammonia that all those beneficial bacteria simply can not keep up. This can result in a spike in ammonia levels.
It is recommended to use a liquid test kit to test the levels as a strip test may be inaccurate. This will tell you exactly how polluted your water is so that you know the extent of the problem.
This will also tell you if you need to clean further or change the water in the tank. There should be 0 ppm of ammonia and nitrite, as well as no more than 10 or 20 ppm of nitrate.
Complete a Partial Water Change
Performing a partial water change is the quickest way to remove pollution from the water caused by the dead fish.
As you do the partial water change, the fresh clean water will dilute the pollution that is left in the tank allowing beneficial bacteria to break it down.
With more severe ammonia levels, frequent water changes will need to be done to remove pollution from the tank.
Related read: Should You Perform A Water Change After A Fish Died?
The amount of water needed to be changed will be determined by what your test kit reads for ammonia levels. When figuring this out you will need to bring the ammonia levels to below 0.25 ppm.
For example, if your test reads that you have 0.5 ppm for an ammonia level you will need to bring that down by half. Therefore to remove half of the ammonia levels you will need to remove half of the water.
Typically it is a general rule to do water changes at about 20% at a time, if more is needed then it would be best to space it out and not do it all at once.
As this can cause stress on the rest of the fish in the tank and can lead to their death.
Add Beneficial Bacteria to the Tank
After you have done the adequate amount of water changes needed to lower the ammonia levels in the tank, it is best to add a beneficial bacteria booster into the tank.
As previously mentioned when a fish dies it gives off a lot of ammonia which the existing beneficial bacteria can not handle.
The beneficial bacteria will also be depleted as the water changes will remove some of them from the tank. So you will want to replace those beneficial bacteria with a booster or a starter.
Boosters, like starters, contain live beneficial bacteria to convert ammonia into harmless substances.
Investigate the Cause of Death
After you have removed the body and taken care of cleaning the tank, it is best to figure out how the fish died.
This is important as it may be an issue with the tank environment, care received, or disease which can lead to more deaths later on.
If the water quality was fine before the death of a fish you will want to first examine the body. This can help rule out causes and determine the right one.
Common reasons why a fish may have died besides poor water quality:
- Old Age – If upon examination of the body and there are no signs of an underlying issue it could mean that they simply died of old age. Most fish have very different lifespans, some only live for about one year.
- Stress – If there is nothing abnormal on the fish body but they are young they may have died because of stress. If you happen to have noticed abnormal behavior in the fish before its death, it may have been stressed out. Some fish can become stressed out easier than others. The fish may be stressed because of their environment or even a bothersome tank mate. When a fish becomes too stressed out it can lead to their death.
- Diseases- If the fish died from a disease there are indicators you will notice when examining the body that were not there before. Some signs of disease are scales being out of place, white spots, patches of discoloration or even bloating in the abnormal belly. Depending on the indicators found on the body, you can figure out what disease caused the death. This can help prevent disease and death in the rest of the tank from spreading disease.
- Thermal Shock – Fish can go into thermal shock when there are sudden temperature changes to their water. Typically when adjusting the temperature in your tank it is best to do so in increments over a few days time to allow your fish to adjust. If the temperature drastically changes in a short amount of time the fish can die due to thermal shock. This can be due to a malfunctioning tank heater, whether it may need to be replaced or maybe it was accidentally unplugged. New fish also need to be acclimated to a new tank.
- Injuries/ Aggressive Tank Mates – When examining the body if there are injuries they could be the cause of death. Depending on the kind of injury, it can be a different cause of death. Injuries such as bite marks can suggest a tank mate was the cause of death. Some fish are more aggressive and may attack more docile fish.
However, if the tank mates are also peaceful in nature and not known to be aggressive then that can indicate a problem in the tank.
A fish may show signs of aggression that are abnormal for them if they are stressed or not happy with their environment.
Injuries on the body could also indicate a safety hazard inside the tank environment. Such a safety problem could be from sharp substrate or decorations.