They can be pretty nasty (for a tiny fish). With having just two, they might try to fight if theres not enough room. I use the biggest tank I can with them (55-up) with lots of cover. Some small dithers would not be a bad idea either. Water quality is also a issue with these (and most dwarf pikes). Keep it clean. So heavy filtration is a good idea. With them being wild cuaght, they might still appreciate softer water. I kept mine in tap water(conditioned) but they were all captive breed (the fry were all acclimated to tap water after about a month) . A lot of wild fish won't spawn in the aquarium without their native water conditions. Others will disagree with this. But if you don't plan on breeding them your tap water should be fine. Some R/O wouldn't hurt though.