goes very well. me and a friend do it and never had problems. when i threw in my young fire eels at 7", my lapradei was around 14,5" and never touched them. Now my eels are bigger and never touch the lap. In my other tank i have a 20" fire eel with some 9" ornates and never any problems. My friend has 20" armatus with 10" endli and no problems either. The only thing that could happen is that the poly will eat a small eel, but if you buy them big enough...