> I started treating the first tank with some malachite green.
Unless you have wierd fish that are sensitive to certain cures (like maybe
loaches), there is only one good cure for ich (well, there are many
actually, but this is my favourite). Quick Cure Ich, kills them in three
days. I've used this on a number of fish now and it does a blitz krieg on
any white spot I've ever had. Don't waste your time with anything else.
Cheers
Peter