He has two posts on this and still won't say why crabs won't work, he just keeps saying my fish will eat crabs. But then says he needs to know large crab species. Then he said he doesn't have algae problems, it's waste.
Please post some pics, and details so that people on here can help you. I am not saying that I can, but a lot of guys on here have a lot of experience, like Melosu up there with 12 years in this hobby.