My name is Tami. I have a 70 gal. I have had set up for years. I have a big feather fin cat, an assortment of tetras, a pleco, and a betta. No problems except the last year I have been dealing with green hair algae. 2 weeks ago after try after try to get rid of it I said forget it and emptied all but 20 gal or so and got rid of all rock and plants(fake) and decided to start over. Added new rock substrate, plants (fake), and water. Fish were doing great. Tested water 4 days ago. Except for ph being about 6 everything was normal. 2 days ago had a dead fish. Ok, it happens. Today almost all fish dead. Feather fin was in bottom of the tank laying there. The 4 fish that were left have white cloudy eyes. The only other time I had this happen I added untreated tap water but fish died immediately. The only thing I did different this time than I have ever done was added 3 nerite snails to help with any left over algae. 2 snails died within days. I thought ammonia toxicity but not really any symptoms. I got the fish out of the tank. Did a 50% water change and have my fingers crossed my fish live. Can anyone give me any ideas on what it may have been or may be if not ammonia? And if it may be something treatable for my fish? As I said they apparently only have white cloudy eyes and some lethargy. I have had my feather fin for 7 years and really dont want to lose him.