I'm looking to stock my new 30G tank. Here is my ideal fish(that I dont expect to exist)
Ideal Fish:
Will do fine in a 30G, maybe even be able to have a pair.
Can eat other fish, like small/medium guppies to small goldfish.
Either be very active or be able to have a medium sized school of 5 or so that it wont attack.

So now that i'm done being unrealistic here's what i'd like. I want something that can feed off an occasional guppy/mealworm treat as I raise mealworms for fishing bait anyways and I have a 10G breeder tank producing guppies. It doesn't really matter if i'm only able to keep just this one fish as I understand a 30G tank isn't going to be necessarily ideal.

Thanks in advance

check out exodins aka buck tooth tetras. U could keep about 15 or so in the tank. They are pretty bad @$$ and are like lil pirahnahs that stay about 3"

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my 75g build---->http://www.aquariumforum.com/f45/fin...ild-18272.html
75g beasolbob tank peat moss & safe-t-sorb 5congo tetras,2bristle nose plecs, 2 German blue Rams

Would they be able to eat a medium sized guppy when they reach adult size?

Yup they swarm them like pirahnas do. YouTube - Broadcast Yourself.

__________________
my 75g build---->http://www.aquariumforum.com/f45/fin...ild-18272.html
75g beasolbob tank peat moss & safe-t-sorb 5congo tetras,2bristle nose plecs, 2 German blue Rams