you need a gold wolf (hoplerythrinus unitaeniatus) or a red/rainbow wolf (erythrinus erythrinus) if you're looking for activity. the hoplias mal (common wolf) won't be very active and will kill your tats for sure. the gold and red wolves may or may not. mine fight among themselves but generally get along with tankmates unless they get really hungry. the gold is the most active but i didn't feed mine for two days and one them ate my 7" gar. the gold wolf was about 7.5-8" at the time.