Really ACs shouldnt be in anything smaller then a 55 gl cuz they get to big around 6- 7 inches and with not much room to get away from each other so you will have lots of fights on your hands. Also they need lots of caves made out of rocks to hide which you wont really be able to do in a 30 gl. If you do it make sure you have about 2 males and rest females so it cuts back on the fighting. Also they shouldnt be in with any fish other then ACs cuz they hunt in groups and they will work togehter to hunt down and kill anything that isnt them.I have a 90 gl which I keep and breed ACs and I have tried plecos and sure enough they didnt last a day no matter what size they were. Now all ACs are mean but the Yellow Labs are nicer then most which might be your best bet cuz the dont get as big.

Hope this helps and good luck.