no test kit, no copper. period. NEVER anyhow dose copper. even if your fish dont die from the exposure, they will be severely damaged if the copper is in dangerous levels. Some fish may be able to take it, SOME. If you have certain angelfish/butterflyfish, copper is a definate no. Some species are very vulnerable to copper. Overall, im not a big fan of copper. The margin of error is too slim. Too much, ur fish die. Too little, its ineffective. Best to get a test kit