I think Chi Ma is using one for his fish tank.
I think I saw a few At Jon and Cat Billing's place but theirs were blue.
They are a wee bit shallow for a fish tank in my opinion and a wee bit deep for a grow bed. But if you can get them for a price similar to an IBC, sounds good to me. (same rules apply as for the ibc as to what they contained before, want to avoid toxic chemicals and stuff.) And you of course want to inspect them (just as you would with IBC's) to make sure they are not too old and brittle (make sure you can't put your fingers through the plastic because it has been out in the sun for too many years ya know, and make sure they don't have holes in them or are vented and stuff.)