i think and believe that having different pikes's together is fine long as u have other fish of size in there with them,but im going off wat i have been able to pull off but none of my pike['s are full grown yet so only time will tell
thanks guys and its working for now but i want decorate better in the 90 and until i get rid of some of the fish i cant cause i have to provide hidding spaces for most of the pike's to keep the peace