Hi all. I’ll try to keep this succinct while giving all info... i have a (too small) 24l tank with 3 variatus platys, 3 gold white clouds and 3 white clouds, and 1 cherry shrimp. Had fish for a year. New 60l tank is on its way in next few days. running a HOB filter with carbon cartridge removed and replaced with sponge as I’m treating (see below) Using test strips at the mo while I wait for master test kit to arrive so I’m aware they’re not too accurate: ph 6.8, ammonia 0, nitrite 0, nitrate less than 10, GH less than 14, KH between 3-6. Just one of the gold white clouds is sick. For past 4 days she struggles to swim so lies on bottom of tank (she does try occasionally and manages to reach the surface but then sinks again and occasionally moves around bottom of tank), isn’t eating. I can’t see any discernable problems of rot or fungus, and ALL the other fish and shrimp are fine. I’ve been advised by a local aquarist to treat whole tank with ESHA 2000, but two days of treatment and no improvement. 25% water change 3 days ago and about 15% changed yesterday, Dechlorinated and added small dose of filter boost as I’d changed to the sponge. please does anyone have any advise on how to save her? The tank is my sons but basically mine as I do all the care and attention, and I’ll be gutted if I haven’t done everything I can.