Sick Fish

If your fish show any of the following signs:

  1. Sluggishness or altered behaviour.
  2. Clamped fins – ie fins not fully extended.
  3. Isolation – hiding itself away, when this is not it’s normal behaviour.
  4. Flashing or glancing – where the fish will try scratching itself against an object.
  5. Breathing changes – such as breathing air from the surface of the water or rapid breathing.
  6. Skin lesions, spots or strange patches on body of the fish.
  7. Loss of appetite.
  8. Looking pale and thin.
  9. Damage, discoloration or blood on the fins

Check out the detailed fish diseases on the common fish illnesses page.

Sick Fish? Don’t Panic!

1. Quarantine sick fish by placing them in a separate tank with filter, heater and make sure it is bare.

2. Diagnose the fish using an online guide.

3. Buy medicine or treatments recommended.

4. If you have carbon in your filter, remove it. Carbon can filter out medicines and make them useless.

5. Measure your tank in litres then place the appropriate dosage into the tank as instructed. 5. During this time don’t stress the fish with loud noises, movements etc. let them rest. Also be careful which fish you quarantine together as one fish may threaten the other.

6. After the fish has healed, wait a further week to see if there is any re-occurrence of the symptoms, before returning the fish to the main tank. A good period of time is 30 days or more in quarantine.

7. Determine the causes for the disease so you can prevent it from recurring. If you cannot determine the cause then increase the rate or quantity of water you change per week. Make sure the water you change has been left for 24 hours before adding to the tank. Try buying a stronger filter.

Also it would be wise to quarantine newly bought fish before introducing to an established tank of fish.



2. Ich/ White Spot Disease

  • Fish has little white specks all over her body.
  • Scratching against tank glass, ornaments, plants etc.*
  • Highly contagious
  • Easy to cure with Ich meds- Mal Green or Copper
  • Brought on by stress and colder water temperatures
  • Raise tank temperature to 80F
  • Parasitic disease

3. Dropsy

  • Extreme bloating not caused by overfeeding
  • Puffy scales that stick out like a pine cone as many say
  • Difficult to treat, contagious!
  • Treat with antibiotics in food

4. Fin Rot

  • Bacterial infection destroying fish fins
  • Caused by stress, bullying, bad handling, poor water conditions
  • Change aquarium water
  • Melafix or other antibiotics

5. Nipped Fins

  • Fins are missing or have torn bits*
  • Usually will grow back in a week or two if fish are healthy
  • Caused by incompatible tank mates, aggressive fish, pecking orders
  • Can be fixed faster with Melafix
  • If it doesn’t stop after a week or two, separate fish.

6. Fish Tuberculosis (TB)

  • No cure, fish must be euthanized
  • Ulcers, bleeding*
  • Lethargy*
  • Loss of appetite*
  • Curved back, weird swimming angle
  • Extremely skinny, empty stomach*
  • Scales fall off*
  • Fins get frayed as if something bit it*

7. Velvet Disease

  • Sprinkling of gold/yellow dust on fish
  • Parasitic disease, much like Ich
  • Can be treated with Methylene Blue and acriflavine

8. Pop-Eye

  • One or two puffy protruding eyes
  • Cloudy eyes = bacterial infection
  • Might be caused by poor diet, bad water conditions

9. Ulcers

  • Spots of blood INSIDE fish’s body*
  • Is a side-effect of other diseases such as TB

10. External bleeding/wounds

  • Spots were scales came off and there’s blood/scab
  • Caused by aggressive fish, bullying
  • Can be treated with Melafix
  • Separate fish
  • Reduce as much stress as possible
  • Change aquarium water often

11. Gill/Skin Flukes

  • Rapid breathing*
  • Constant scratching/rubbing against aquarium & decorations*
  • Red, inflamed gills*
  • Gills wearing away
  • Fungus/Mucus across body*
  • Parasitic disease
  • Sometimes you can actually see the little hooked worms hanging off the fish’s side or gills (ew!)
  • Look like thin black threads

12. Fungus Rot/ Mouth Fungus

  • Cotton-y, wool like tufts hanging on fish’s body, esp. mouth in the case of mouth fungus
  • Sometimes look like white spider webs
  • Loss of appetite, lethargy
  • Treat with Fungal meds – Pimafix etc.

13. Hole in the Head Disease

  • Parasitic disease
  • Holes in head, along fish’s back
  • Caused by nutritional deficiencies – you should improve fish’s diet!

14. Swim Bladder Disorder

  • Very common
  • Fish doesn’t swim properly, wobbles*
  • Sinks to the bottom or uncontrollably floats to the top
  • Caused by constipation, overfeeding or infection
  • If it’s just constipation or overfeeding, it should heal in time by itself
  • Feed fish peas and veggies to promote digestion