Warning Signs
By Yechiel Kuperman, marine biologist · 49 years keeping fishTold by Captain Cory — Cleanup Sergeant
“No pellet left behind — and no warning sign, either. A fish that is unwell will tell you. You simply have to know how to look.”
Fish cannot tell you in words when something is wrong. But they show it — if you know what to look for.
- Gasping at the surface: Usually means low oxygen — check the filter and aeration first.
- Fins held close to the body: Healthy fish hold their fins open. Clamped fins mean something is wrong.
- Hiding more than usual: A fish that has stopped coming out at all may not be feeling well.
- Not eating: A fish refusing food for more than a day or two is telling you something.
- Rubbing against objects: A fish scratching itself against rocks is uncomfortable — check the water.
- Sudden colour change: Happy fish have bright, steady colours. Dull or pale means stress.
- Spots or unusual patches: Any new markings that weren't there before — ask a knowledgeable adult to take a look.
- Swimming sideways or listing: Needs help quickly. Tell a knowledgeable adult straight away.
- Several fish unwell at once: Almost always the water. Check the water first.
⚠️ When fish seem unwell: check the water first. Always. If the water is fine and the fish still seems unhappy, ask a knowledgeable grown-up for help.
Yechiel's Rule
Look at your fish every day. Learn their normal — then you will notice when it changes.
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