First time fish owner, I adopted this 75g with its 12 guys, inverts (cories, plecko, snails) and fish (glofish). about half the glos got Ich, i didnt notice until it was severe, I thought they were air bubbles??? When we realized we rushed to local fish store, she gave us "rid ich" said they use it with all their fish, totally safe. For 75 gallons, she said, a cup and a half for 4 days. we were in a panic, trusted her didnt ask questions ran home and dumped a cup 1/2 into the tank. the water was so dark, and there was visible stress, but along with online research this was the solution and i just thought well of course they dont like it but they need it! starting at 1 hour in one died, within 12 hours we had lost the entire tank including 2 new glos of 3 days who were obviously the most healthy. We are assuming our dose was off, we cant think of how else this could happen. We are devistated and feel so terrible for the fish we had grown very attached to, they deserved better. someone please give me some advice, i have no idea what went wrong or what i should have done.