neon goby would be food. Your best bet is hypo. Copper and malachite is a rough treatment for puffers. Lower the SG slowly let if sit that way for around 2 weeks. id go for around 1.010 to be on the safe side. if your DT has no inverts, urchins, stars etc..... then this will be safe for all your fish. Just dont go too low for long durations of time. When the ich is gone from the DT, start to slowly raise the salinity. Little by little in this case means over the course of a week lol. This will help keep the stress away from the fish and make them less vaulnerable to reinfection. also during this time, feed them well to keep the strong and healthy.