I have the 8" block in my sump. Absolutely love it. I was able to feed super heavy with 2 leopard warsses and a tamarin wrasse along with 4 other fish in a 66g tank with zero issues. It was a mixed reef and all the things you read about it leaching Al to me is unfounded. I know many people that run these without issue. Yes there is a correlation with titron test and these but nothing has been proven definitive. I would not worry...