Very true! I used pea gravel mixed with river stone because I wanted the denser surface area the pea gravel provided. If I had it to do over, I would have gone 100% river stone! Despite a proportionate fish weight to filter ratio, mechanical filtration and settlement tanks, I have had to clean out tilapia turds clogging my growbeds twice in the past few years. That is one NASTY job1 The larger diameter river rock is much less prone to clogging and easier to clean if it ever does.Originally Posted by Oliver