I have an 18 gallon tank. Recently I started noticing fish were getting rounder, putting on weight, scales protruding, red spots in the stomach area and deaths. I am sure its DROPSY disease. How can I treat it? I have a well balanced tank change water twice a week each time 25%, I have Co2, temp.23-24 with chiller, use RO minerals added to raise TDS, no algae, snails are fine. Two weeks ago I added 5 ottos may be they triggered the disease coz 2 of them died within a week. I have rare mosses in that tank so I cannot use just any medicine coz it has to be plant and invert safe. Therefore I have few options. What can u suggest to treat the Dropsy problem? I have right now in the medicine cabinet for fish only JBL Furanol 2 and Seachem Paragard. What is better to treat this disease? Please help guys my fish who are more than a year old have started dying like crazy this never happened to me before.