Hi. I have a 30 or 40G long...and when i wuz looking...all of my black neons have white dots on them. The other fish like corys, and glo lights didnt have any on them. I treated it with ick jungle medication...using only 2 tablets which treat 20 G. This morning, i saw alot of those whtie dots off the black neons but i found one of mi panda corys dead. I bought melafix and wuz wondering if it is good. should i use it half strengthed? do a water change before adding it?will it be ok if i am not able to remove the carbon from the filters. i also have 2 opaline gouramis in their.