I know it’s been awhile without a reply but I think I can help. Im sure you can mix the eco complete in it but I have also had a lot of success putting a layer of plant Substrate under a layer of sand. I haven’t personally used eco complete so I don’t know how messy it is but if it has soil In it, the sand cap will keep the dirt from being kicked up every time the water is stirred. You might like the look better and it would concentrate nutrients at the plant’s roots.