it seems like you want either a cichlid tank or a piranha tank. either way is good in my book u just have to remember that water quality is a must in either setup. if ur just sitting waiting for a fish to put in the tank search your local fish stores for large plecos, or catfish. scavengers are a must for a tank this size. then set up 3 airlines for a start. piranhas need high oxygen content while cichlids need high ph. no undergravel filters like i have tried try the cichlid sand substrate. it keeps the ph high the way they like