The op is looking to create a denifrication chamber with this "sand filter". Just sayin this thread went in sideways direction ( as most do lol). anyone thus far have any ideas how he could use the very nice chamber he has to achieve his goal? I'm not up on the subject enough to comment much because my goal is to understock to avoid all those headaches....except to say that anaerobic bacteria need just that, no oxygen. so how does he acheive that in the chamber besides low flow?