I had a thread earlier because I had lost some fish...thanks to @Demeter ..we figured it down to parasites (tank is newly cycled maybe 1 1/2 months?) No more white stringy poop.Anyway, things were going good...after the second treatment with General Cure.. I did a 35 % water change and put in a 1/2 sheet of poly to soak the meds out. About three days later I lost my opaline gourami...the behavior changed ( he/she was kind of star gazing? Sorry, goat terminology...but staring at the duckweed in the top of the tank, head up, tail kinda down) This lasted one full day and it died. Before this, it was acting great and eating great...then it stopped eating, and started staring at the top.When I removed the fish, one eye was very black. I now have a female guppy laying on the gravel and kind of flopping around...big belly....front fins look to be immobile? She seems to be weighted down?This is different behavior than any other of the fish that have died. Did I leave the poly in too long? The bag didn't say how much to use or how long to leave it so I used half a sheet and left it until it discolored to a light brown and removed it after three days, which was tonight. Tested my water and here are the stats... PH (regular test) 7.6 (High PH test-8.4) Ammonia- 0 Nitrite-0 Nitrate-0 Hardness is unknown There are no live plants in my tank, nor any driftwood,etc. The only live "plant" is duckweed. I have 5 platy's, two mollies, 4 mountain minnows , 4 guppies , 3 neon tetras. Again, the tank is a 55....I feed Omega One flakes and frozen brine shrimp. I have lost, 2 lyre tail mollies, one black mollie, 7 neons and now the opaline gourami. The lyres, and mollie died most likely from the parasites, the neons were victims of newly cycled tank, and the remaining three look good so far.....and I have no idea what happened with the gourami I appreciate any help you can give me. I have never had this kind of trouble with a tank! I have successfully raised Convicts and bred them too, and have had fish for years ranging from goldfish to tropical small fish to cichlids.... One thing I forgot! I did have the filters out of the HOB filter for parasite treatment...they were put in a bowl of tank water and sat idle for three days, ( was that bad?)I then put one back in and a new one back in along with the poly.