Trying out scoria as a medium. Very rough edges and dirties the water so much but I don't think this will be much of a problem. This stuff is cheap however I do intend to invest in expanded clay. Also important to note I thought I might be a good Idea to place the bell siphon at the back out of the way, a decision that I am now regretting, I hope nothing goes wrong with this before I set up the remaining grow beds.