Population control in a soft water tank

[Leo2o915]

Have a lot of guppy fry and young guppy’s can’t catch them all want a smaller type predator fish to control the population prefer South American fish that won’t mess with plecos 

[AnimalNerd98]

How big is the tank and how warm is it being kept? 

In terms of South American fish, most adult fish will go after guppy fry (if they can fit them in their mouths). I thought of either Apistos or Ram cichlids. For electric blue rams, they need to be kept on the warmer side as opposed to Bolivian rams. 

If you want to go with fish from other places, you can consider bettas, gouramis, even an African dwarf frog. 

In the long run though, you might want to just keep males and/or selling off babies as feeders to your LFS for some store credit. 

[JettsPapa]

You could get a few female albino koi guppies.  They're relentless fry hunters.   I've had three of them in a moderately planed 5.5 gallon tank on my desk at work for over a year.  I've seen exactly one fry, and I never saw it again, and I've seen other reports of similar behavior.