I need to know what typw of fish will eat guppies and fit in a 20 gallon tank but

[StephanieF]

wont eat my other fish.? I have 6 teras, 1 male betta, 2 algea eaters, 1 molly, 2 adult guppies and 130 baby guppies. I dont have the heart to flush the babies and seperate the two adult guppies so putting them in a separate tank is not an option. It needs to be kind of cheap no more then $15 $20 tops. Thanks for your help.
I tried selling my fish to the pet store and they wont buy them