Tree frogs prefer tall enclosures and you are losing lot of air space to your water feature height. Also, be aware that if your frog grabs and eats one of those Pigmy Cories it could be it's end too. Corey's can get stuck in frog digestive system due to it's fin spines.

You can use a 2 in. deep glass bowl (at dollar stores) to feed crickets and they will not escape. Once frog figures out how to get them from bowl; you've prevent insect drownings and can monitor feeding too. Good luck !