In that size tank i would not add copper. Is it possible to get a small 10 gallon tank and do you QT in that? if you choose to do copper it will be easier to monitor the levels in 10 gallons.also when the treatment is over you wont have any long term effects of copper in your main tank.in summary I would not do copper in a main tank that size.I have done copper treatment for years and have had very good results with the correct copper and a small tank. there is too much crap sold that claims to give results.Also have you considered doing Hypo instead of copper?Do a search under the disease forum for hypo.Good luck I hope he makes it...