your shark may be targeted at some point. if your looking for a cat, look at big synos. and if youve got the room, maybe a shovel. but that may be pushing it, (dont knwo how your tank looks). at my store we had gars and pikes for a while, both have amazing personalities, and grow HUGE. pikes get very very territorial though and will try to be the "king" of the tank at some point most likely.