i have a large mbo puffer who how as a large lump on his side and is swimming upside down have started to treat with an antibiotic but has anyone had or see this before

I've not heard of this before, but I have no experience with puffers. What is the treatment you're using. What are your water conditions (pH, nitrite, nitrate, ammonia etc.) That could help.

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I love lamp

Sorry about your problem mate, it is highly likely to be a hemorrhage, lots of mbus get this with older age, recently my lfs lost a 2.5 foot mbu worth a lot of money because of the same problem.

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Dom