I have a 3 month old tank that I waited a long time to get balanced. I have 40 lbs of live rock and sand. After 2 months ph was good, no amonia, nitrites were a little high, nitrates were <.25 temp 80. I added live plants, 2 chromis, 4 crabs and 4 snails. within one week i lost one chromis. everything else was fine. i bought an extra test kit to be safe before buying more fish. for the last 2 weeks I have had perfect gravity 1.025 ph at 8.2 no amonia, 0 nitrites and 0 nitrates so I went shopping. in one trip i added 2 clowns, one tang, and 2 more chromis, a cleaner shrimp and 4 more snails. within 24 hours my cleaner shrimp died and now my original starter chromis is dying. what do i do? if i add ich medicine with copper is it going to kill my snails and crabs?