Short question: Is CopperSafe (Mardel product with chelated copper sulfate) OK to use or does it "copper poison" a tank? Long version: I planted some water irises from my yard pond into my 29 gal freshwater. The outside pond has no fish at all. I've used the irises twice before in tanks but with this planting I began to see what looks to me like flat worms (Platyhelminthes). It would either put its thicker posterior into the soil and sway in the water near the roots or it would undalate/swim in the water. They ranged about 1/4" to 1 1/2" in length. When I picked them up, they did not "attach" to me or draw blood (as I would have expected a leech to do). I am sorry but I didn't take pictures. I took a net and caught them as soon as I saw them and put them outside. I took one to the LFS and they were stumped: flukes or planaria maybe? I don't think they were flat enough in the middle for flukes (and again the pond had no fish). They don't look like planaria to me (no eye spots). So...I have fish in this tank. I've watched carefully for nearly one day and I don't see any swimming worms any more. I have seen one smaller one dug down in the substrate. I am hoping the gourami will eat it if it appears. I'm watching the fish carefully for signs of worms, illness, or being off. If they need treatment, I can move them to a quarantine tank and run the 29 gal fishless. Could I treat them with CopperSafe or would that chelated copper sulfate treatment make the treatment tank unuseable afterward. (I have the impression that some tanks cannot be used because of copper presence.) Advise?