It all depends on the pike. There are some pikes that would just totally whop on all the fish in that tank. And if they don't like the fish, regardless of size, the pikes will beat the living heck outa it. So you may have to do trial and error, if the pike gets along, great. if not, take it back and try another one of the same species. There is a WIDE variety of personalities within the same species of pikes. Some peeps have luck keeping in 'xingu I' with other fish, where as others can't even keep any other fish with them. In a 150gal tank though you should be able to get away with most species of pikes. Saxatilis stay a little smaller, so i would go with that group. Crenicichla sveni is regularly available, beautiful, and not to expensive.