It is not their natural subtrate, but I have a large tribe of Corys and Loaches on EcoComplete, and they do ok. I would imagine that it puts more wear and tear on their barbells, but I have not seen any of mine lose their barbells or get infected barbells. No one has starved. I saw the lady wear hers down really short one time digging in the gravel bits, but a cory mentor told me to watch, and if they did not get infected they would grow back. They did not get infected, and they did grow back.
There are small angular red pieces that I have been concerned about, but after 2.5 years the Corys and loaches in the tank have done fine.
But I must add again, that it does cause them to use their barbells a bit differently than they would in a natual habitat and so you miss the delightful exibition of a Cory barbell created dust up. I am at present considering changing some Cory tanks to a finer sand.
