Rainbow Fish

[reder]

i have a 70 gallon with 12 rainbows in it and i just noticed that one of them has a red sore on its gill. only one fish has it and it looks like it is eating threw his gill. what is it and is it contagious? please help. thank you

 

[Colin_T]

Hard to say without a pic but it could be an ulcer caused by flesh eating bacteria. Ulcers occur when the fish are stressed out and kept in dirty tanks where the build up of gunk encourages disease organisms. A weakened immune system will allow the bacteria to get into the fish and start causing damage.
Rainbowfish need clean tanks and lots of vegetable matter in their diet. If they don't get veges every day and do get lots of meat foods, this can cause ulcers. You can feed them on fresh or frozen (but defrosted) peas, carrot, spinach, pumpkin, zucchini, etc. They also do well with spirulina flakes and duckweed (a small floating plant).

Try doing a 40-50% water change and complete gravel clean each day for a week. Also clean the filter if it hasn't been done in the last month. Add veges or plant matter to their diet each day. If the problem doesn't clear up in the next week or two, then isolate the fish in a separate tank and treat it with tetracycline or something similar. You will probably need a vet to prescribe and supply you with tetracycline. This drug wipes out filter bacteria so you should only use it in a quarantine tank that has a filter with Ammogon (ammonia removing granules) in it. The Ammogon will absorb any ammonia produced by the fish so you won't have to worry about ammonia poisoning.

 

[LauraFrog]

What's the nitrate reading in the tank? Rainbows are very sensitive to nitrate, so if the reading is consistently above 20ppm, you might need to invest in some nitrate removing resin. It can weaken the immune system, leading to problems like this. (I don't know what it is, Colin is probably right.)

 

[drobbyb]

I agree with both. You also need to be doing at least 50% weekly water changes. This keeps your nitrates low and provides the clean water that these fish demand. Rainbows aren't for everybody, but anybody can keep rainbows if they know how. Ask lots of questions! You might try the web address in my signature. It's a forum dedicated to nothing but rainbows and their care and breeding.