No I did not feed it to the fish. It is a liquid medication and it also is not very expensive so I do not see how it is a waste. If you are going to keep fish you have to care for them but like Beasts said, it probably will not hurt him to just leave it as is. However, if the sore does not heal over and "callous" itself, it could turn into a larger open area, which would eventually effect his eating.