I have a 20 gallon with a aqua clear HOB and coop sponge. Stocked I have 4 khuli loaches 1 dwarf gourami, tons of snails, and I had 8 cardinals now down to 6 with one on its way out. One other cardinal had dropsy another had a white ring on its lip and like a fungus now another one has dropsy can’t figure it out no one else gets sick