I have a 55 gallon saltwater tank with a stars and stripes puffer,hippo tang,snowflake eel,picasso trigger and a panther grouper. I would say they are all about 4-5" long. I believe that my tank may have caught a parasite of some sort which could have come from an introduction to a new fish or either live fish feeding (not sure which) I more than likely had too many fish in the tank (hence 4 fish have died) or something else. I have done 2 water changes in 2 days (6 gallons 1 day, 6 gallons the next day) removed my carbon, cut off my UV sterilizer added Microbe-Lift for 3 consecutive days and also a ph buffer 8.2 because my Ph was low. My fish have been gasping for air and I cannot sleep because I am checking them every 30 minutes. Please help me with any advice you can give!!!