the CK may outgrow the del before it outgrows the tank, depending on size. O's can be risky w/ polys, too for the same reason and they can sometimes be aggressive to polys, but is not always the case.BIGtyme;2509643; said:it will be in there with a clown knifefish until the clown knife outgrows the tank, and possibly a oscar, but im not sure, any suggestions as to some sweet tankmates for this guy?