The Puffer Forum

Hello, I need some help identifying what is wrong with my blue spot puffer. I’ve had him for 5 days in a mature tank. He was fine when we brought him home but has developed a large brown/purple spot on his left side. Tank mates are snowflake eel, one spot foxface, 2 clowns, 1 bicolor angel, 1 damsel, and 4 mollies. CUC: snails, hermits, starfish. Haven’t seen any mates pick on him. He has been hanging out in the top of my tank where there is low flow. I have seen the mollies clean him, like a wrasse would clean parasites. Eating normal, just kind of hiding and acting shy. Any advice?

55 gallon
Ammonia: 0
Nitrite: 0
Ph: 8.4
Nitrate: 40
Salinity: 1.024

Heater burn?