well I am not sure. the plastic drums are supposed to be clean there is no smell to them. There was one that I had it did have a smell of fabric softener so I didn't use it. but the rest cleaned up well and no smell or taste from the drums that I can tell.

you know I haven't lost a single fish all the fish are fat and healthy no diseases. the pH test kit I have I bought from a pet store for checking the pH in your fish tank. 5cc water add 7 drops and the blue color chart tells you the pH. when I did it the day I changed the rock it was 7 to 7.5 two days later 9

It may be to sometime is takes a while for the whole system to stabilized and seeing I just changed the rock it could take a while before the whole thing come down again.

if it wont come down by the end of December. I could remove the rock and put a plastic sheeting liner in it and try again. if that doesn't work I give up on using barrels. and try making everything from other materials I know for sure are not contaminated.