Oh and their are different kinds of copper additives some much more toxic than others, cupramine by seachem for example is way less stressful on fish than others I've used and kills ich at .03 ppm(might have to go higher for other ectoparasites like velvet not sure) even though the recommended dosage is .05. I know lots of people that run it all the time in their FOWLER tanks, I do myself in my 100 gallon, the only real drawback is if you want to run a skimmer you'll have to test and continously keep your levels up with redosing as it will not only be pulled out by carbon, and cuprasorb, but by a good protein skimmer also(they don't tell you that on the bottle but will if you call them). That is also why your commercial systems by marineland use giant biowheels instead of skimmers keeps the chemicals in the water so pet stores have an easier time treating in their displays. At .03 even alot of real copper sensitive fish aren't bothered by it in fact after I switched that 100 gallon over to FOWLER and cupramine I found my serpent star still in there 3 days later, he turned white and was barely moving but he recovered once he went into another tank so it must be pretty gentle for copper. I was kinda mad when his color returned he looked pretty cool white. The only fish that I've ever thought might be bothered by cupramine is a powder brown tang, I've had 2 of them that started looking real fallow and skinny while in cupramine and started looking better when I got them out, but it could have just been coincidence.