Please post the water quality numbers
for your tank. Please include pH, NH3
. How do you prepare your SW
for water changes?
Buoyancy issues can be caused by a great many things but if there has been nothing new added to the tank or the puffer has not been physically damaged, foods fed are the leading cause. Either too old, improperly stored or the wrong type altogether. They can lead to blockage or bacterial infections.
So far what you are describing sounds like a toxic water situation. Please answer as many of these as possible....