This company values misleading people. Consider chemically attacking weeds vs the mechanical method. The chemicals (copper sulfate) is really good for fish. Cleans the gills of invading nematodes, and cleans them of bacteria (gill disease). Like emphazima, your fish are choking for oxygen. Clean them periodically with the chemicals, and you will have healthier more roboust fish. So when Oakland Harvesters website claims chemical treatments harmful or Toxic, they are out right lying to you. Until they can speak with truth, avoid this company. The lies will just compound.