Common Fish Diseases and How to Prevent Them
Ich, fin rot and swim bladder problems, and the water-quality habits that stop all three.
Nearly every common aquarium disease is opportunistic. The pathogens are usually already present; they only take hold when water quality or temperature stresses the fish.
White spot (ich)
Grains of salt scattered over the body and fins, plus flicking against decor. Treat by raising the temperature slowly to about 28°C for two weeks alongside a proprietary treatment. The parasite is only vulnerable in its free-swimming stage, so complete the full course.
Fin rot
Ragged, receding fins with white or red edges. Almost always a water-quality problem. Test for ammonia and nitrite, do a series of water changes, and it often resolves without medication.
Swim bladder problems
Fish floating, sinking or swimming at an angle — common in fancy goldfish and bettas. Usually constipation or gulped air from floating food. Fast for two days, then feed a deshelled cooked pea, and soak dry food before feeding.
Prevention beats treatment
- Test ammonia, nitrite and nitrate weekly. Ammonia and nitrite should always read zero.
- Change 20–25% of the water weekly with dechlorinated, temperature-matched water.
- Quarantine new fish for two to four weeks.
- Do not overstock, and do not overfeed.
