yellow powder

Hi Mr Pat, will the yellow powder kill the bio-bact in the filtering system?
One of my CBR has concave gill cover while the other side is normal. Suspected bact infection..

I think it will. Preferably stop your bio filter and just use medication with sponge filter and airstone.

If your fish is sick, you should treat the fish outside your main tank. A large laundry bucket would suffice, but make sure that you measure the medicine properly. The antibiotic that you have is quite potent, but make sure that you do close the pond so that you do not get any sunlight. (And you should keep the packet away from sunlight, too.) Do not forget to also add .5% of salt too.

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Thanks for your input.

Mr Pat thanks for your valuable advice.