Belly-Sliding Fish Fry: What Does It Mean?

Updated on October 23, 2019
Bunniez profile image

I have experience breeding betta fish. I enjoy sharing my expertise with other breeders.

Healthy fish fry swim normally.
Healthy fish fry swim normally. | Source

Why Are My Betta Fry Not Swimming Normally?

Fish breeders will notice that healthy fry swim about in the tank from the moment they become free-swimming. Other fish fry sink to the bottom and slide about on their bellies, picking up food from the bottom as it falls there. This may seem like fairly sensible behavior for fry, but it is usually the first sign of swim bladder disorder. In most fry, it means that culling is the best solution.

What Causes Swim Bladder Disorder?

Swim bladder disorder occurs in baby fish fry when the organ that controls the swim bladder fails to develop properly, leaving the fish unable to swim normally. Some fish do develop swim bladder problems later in life, often due to overfeeding or illness, however, the type of swim bladder disorder that is seen in fish fry is a chronic, lifelong condition. For this reason, belly-sliding fry should be eliminated from the breeding population and preferably from your fry tanks altogether.

What Are You Feeding Your Fry?

If large numbers of your fish become belly-sliders, you may want to look at the types of food they are getting and the condition of the tank water. Feeding BBS or baby brine shrimp is often associated with swim bladder disorders in fry, though some breeders claim that feeding baby brine shrimp has no negative effects at all.

Healthy Betta Growth From 1 Week to 6 Months

Baby Brine Shrimp and Water Quality Issues

I can say that in my own experience from breeding betta fish, spawns fed extensively on baby brine shrimp certainly do have a higher rate of belly-sliders than spawns fed extensively on other foods like micro-worms, in which instances the fish seem to develop other issues like missing ventral fins.

How to Prevent the Condition

Here are some basic husbandry rules to follow:

  • Offer clean water: It is incredibly important that your baby fish fry have clean water.
  • Clean the brine shrimp: Baby brine shrimp should be cleaned of their eggshells before being fed to your fry.
  • Consider egg yolk: You may even find that you get better results with egg yolk rather than BBS or micro-worms, although breeders who only use egg yolk often find that their fish grow more slowly and have a lower survival rate than those fed on live foods.

When Culling Is Kinder

If you have belly-sliders, give them a few weeks of good, clean water and good food. If there is no improvement and your fish are confirmed belly-sliding babies, there is very little you can do. Some recover partially to have some swimming ability, but unless you have room in your tanks for several fish, without proper locomotive skills, it is kinder to cull them. As they grow, swimming may become increasingly difficult, so culling is the best and kindest option you have.

This article is accurate and true to the best of the author’s knowledge. It is not meant to substitute for diagnosis, prognosis, treatment, prescription, or formal and individualized advice from a veterinary medical professional. Animals exhibiting signs and symptoms of distress should be seen by a veterinarian immediately.


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    • profile image


      18 months ago

      You're misusing the word "culling". "Euthanizing" is the correct word here.

    • profile image


      8 years ago

      i speak birds its my life but i have two fish tanks my goldfish are breeding my other tank i have sun burst platy ,african dwarf frog, and a snail

    • profile image


      9 years ago

      Great articule, I was wonder about some ram bally sliders, since I have everything controlled but a few of them are bellysliders.


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