I have 100 gallon and a 55 gallon tanks. The 100 is about 6 months, live rock and sand, and 55, no live rock or sand, is almost 3 years. I treated the 100 with Ich medicine about 3 months ago, it killed all the fish. I emptied the tank, left a little water, refilled, left it empty for about 3 weeks, it recycled. All perimeters were good. Every time I would add fish they would die in about 2 or 3 days. Left empty again for about a month, adding fish again, some are dying a couple are still alive. I had the water tested by a lab, ( only problem Phosphates high so I treated), even though I use the same water in the 55 gallon. I have a couple shrimp and some hermit crabs and an anemone, they are all okay. I can’t figure out what is wrong with this tank. My 55 gallon has never had any problems. Could the Ich medicine have contaminated the tank somehow, like absorbed in the tank sealant? It was fine up until the Ich medicine was added.
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