Dead Fish in Tank: Here’s What You Must Do

Sadly, sometimes, fish die. It can be upsetting and unsettling to find a dead fish in your tank. 

The biggest thing to remember is to stay calm.                                                                                                                      

Today, I’ll go over the steps you should follow in the unfortunate event you find a dead fish in your aquarium. 

What to Do if You Find a Dead Fish in the Tank?

Remove the Fish

Get a net and remove the dead fish from the tank.

Bacteria and saprolegnia can grow on the carcass of a dead fish. Not to mention, the body will produce extra ammonia as it rots.  

And, other fish in the tank will likely start to pick at the dead fish. If the dead fish was sick, this could pass the infection on to its tank mates.

You want to get that carcass out of your aquarium as soon as possible.

OK this is going to sound gross, but if the fish’s body is falling apart, do your best to get all the pieces out of the tank. If you need to, you can suction them out with your gravel vacuum.

Look at Your Other Fish

Once you’ve got the dead fish out of the tank, take a really good look at your other fish. Look for signs of sickness like:

  • Cloudy eyes
  • Bulging eyes
  • Ragged fins
  • Abdominal bloating
  • Body tilting
  • Clamped fins
  • Floating at surface
  • Sitting on substrate
  • Red sores
  • Tufts of white cottony stuff that looks like bread mold growing on the fish
  • Lethargy

If you see any of these signs, consult a veterinarian that specializes in fish.

Here at ModestFish, we’re dedicated to helping our readers keep healthy and happy fish by presenting the best practices that have helped our own tanks thrive for decades. But, we are not veterinarians and can’t give you veterinary related advice. Our firsthand experience with raising fish can’t replace the advice of a medical professional. Please, seek out professional pet healthcare resources, if you think your fish are sick.

Check Your Water Parameters

Poor water parameters are the root cause of many fish illnesses and deaths.

It’s always a good idea to test your water after you’ve lost fish. Especially check for ammonia, nitrite, nitrate and pH.

Basic parameters should be:

  • Ammonia – 0 ppm
  • Nitrite – 0 ppm
  • Nitrate – <30 ppm
  • pH – Ideal pH varies by species and location, but it shouldn’t be significantly different from your tap water.

For more information about aquarium testing kits, see our in-depth article here If your testing detects ammonia or nitrite, I would recommend immediately adding a dose of Seachem Prime, which will detoxify the ammonia and help fish tolerate high nitrite and nitrate levels in the water. Always follow the manufacturer’s dosing recommendations.

Do a Water Change

If you have poor parameters, or if you just haven’t done one in the last week, I’d recommend doing a water change and cleaning the substrate really well.

This will remove wastes and replenish any depleted minerals in the water. At worst, a water change really can’t hurt anything. And at best, you’re removing harmful substances that are stressing your remaining fish.

I generally perform 50% water changes on a weekly basis. But, if it has been a very long time since you have done a water change, it’s best to change out 25%-30% each day until conditions are back within acceptable levels.

Don’t Be Too Hard on Yourself

And look, if you lose some fish, don’t beat yourself up about it, it happens. 

I’ve been keeping aquariums for almost 25 years at this point, believe me, I’ve lost fish over the years.

And sometimes, you check everything out and your water is great, and you end up having no idea why you lost a fish or two.

It’s awful, but don’t take it personally. Take that crappy feeling of guilt and turn it into energy that you can pour into aquarium maintenance. 

You don’t have a time machine (if you do, I have a list of things I need done. Contact me immediately). You can’t change what’s already happened. 


Losing fish is never fun. Some people might not understand, but aquarists put a lot of time, effort and love into their tanks. 

It can be really upsetting to lose fish. It’s important to stay calm, remove the fish,  check everything out and take action if necessary. 

Oftentimes, you can never pinpoint why a fish died. Sick fish are often bullied and driven away, so many species have adapted to mask any sign of sickness until they are terribly, terribly sick or even near death. 

Sometimes, it can be next to impossible to even tell a fish is sick until you find it dead in the tank.

Don’t rake yourself over the coals. Just do your best to take care of your tank:

  • Weekly 50% water changes
  • Always condition water you add to the tank
  • Don’t overfeed
  • Maintain a steady temperature inside the tank

Just these basic things can go a long way to keeping your tank inhabitants happy and healthy.

I hope you find this article helpful.

I wish you and your fish the very best!

Katherine Morgan
Katherine Morgan

Hey, there! I'm Katherine from Northwest Florida. An aquarium specialist, I've kept tanks for over two decades, enjoy experimenting with low-tech planted setups and an avid South American cichlid enthusiast.

One comment

  1. Terrific info on this feed, Thanks. I should have researched b4 buying 2 little comets yesterday for my new used 5 gal BiOrb. Don’t worry, a friend has a pond; I’ll call her next. Hope I find something to survive in 5 gal. L

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