You do know that they are found in a varying range of grades in the wild, from sand to gravel? (Axenrot and Kullander, 2003,Casatti, Lilian, et al 2010) free at this link http://www.corydorasworld.com/img/upload/files/C_%20diphyes%20-%20O_%20mimulus.pdf
Casatti L, Romero RM, Teresa FB, Sabino...