Betta Over-Feeding

A happy betta in his tank

It’s an unfortunate event when one of these shows up on our service. A tiny betta with a large lump on their belly. Of the follow differentials, none of them are any good: over-feeding, Mycobacteria or a tumor. Sometimes, if a fish is cooperative, we can do a quick ultrasound and get a clearer picture. Other times, we do what we can for the only thing we have a chance to fix: over-feeding.

Why does this happen to bettas? We see this quite a bit and most of the time it is preventable. What causes this “giant poo ball” formation in such a small fish? (And no, it’s not “constipation.”)


Too Much Food

Yes, we know betta’s don’t come with instruction manuals. It’d be great if all pets did. The betta food available on the shelves of your local store can be minuscule or half the size of your fish’s eyeball. Everyone loves to feed their fish their love, and many fish, bettas included, will eat more than they should in one feeding.

No matter what pellet size you have, feed enough to take up roughly the same space as one fish eyeball. This will vary from 10-12 pellets to 1-2 depending on your brand! After that, no more! And treats no more than once a week.

Inappropriate Temperature

Since fish are ectotherms, their metabolism is tied to the water temperature. Bettas are TROPICAL and need a heater. If the water is too cold, they can’t digest their diet, no matter what it is. Always make sure to have a thermometer in the tank, and not those stupid “stick on” ones, to make sure your heater is working correctly.


Poor Water Quality

For regular readers, this should have been your #1, and it’s usually compounded with the other points here. Why are bettas kept in terrible water? BECAUSE YOU HAVE THEM IN A $*@^$& BOWL!!! No fish deserves life in a bowl. It is archaic and cruel. Upgrade them to a new tank and stop living in Victorian times.

If they are in a tank with a heater, you’re ahead of the curve. But your water still needs to be within range in order to keep your fish health. This means regular maintenance and water changes! No exceptions.

Old Fish Food

We have never actually seen a betta finish an entire container of betta food. Unless you have more than one fish, you should NEVER attempt to finish it before buying a new one. After 6 months, most of the water-soluble vitamins, including vitamin C, have gone. Push it to a year or two (true story), and you are essentially feeding your fish cardboard. Yum! Replace your food every 6 months and be sure to store it properly!


And sometimes, you may do everything right and your fish still starts filling with food. Since they are such small fish, it’s hard for us to get in there and get down to core issue prior to death. Not all animals are built for a long life, no matter what species they are. If you’ve done everything correctly above, we and your fish appreciate your solid dedication to their care and well-being.

If this happens to my fish, what do I do?

Contact your aquatic veterinarian immediately. This issue should not wait.

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