If you did a pair of thumbnail dart frogs they would eat the gnats. I have some Vents and some Varadero. The Varadero are very cool and out and about often. You have a lot of frogs so I'm sure you understand that proper care is very important to them. I don't usually advise thumbnails to newbies but you're not really new to frogs. The biggest difference is their size and they need very specific environmental requirements that need to be met just like all your other frogs. They only thing is those requirements are going to be different than the other ones that you're use to. Do some research, set up your tank way ahead of time and start getting use to making fruit fly cultures (which are very easy). They are not hard to keep but only you know yourself. If you find that its easy to keep the frogs that you have then you're ready for the next step. If however, you still struggle with the health and care of your current frogs then wait and get some experience under your belt. You're ready when you feel like you're looking for a new challenge. Only you know when that is.