First off, you really do need to remove the lizards. I don't care how long the frog has been around them, two animals of different species trapped in a tank together WILL stress each other out. Problem is a stressed frog looks identical to a calm happy one until it ends up getting sick or hurt. Seriously, no one will say it's a good idea to have them together.

Silversides can be purchased in packages for f/t feeding. Not really an appropriate staple food but good as treats. You probably want to stay away from feeding live fish. Anything coming from petstore feeder or bait stock is almost certainly going to have parasites. Plus, depending on the species many feeder type fish (especially if they have red or yellow coloration) contain thiaminase which can cause brain damage and even death in many reptiles and amphibians.
Mine loves silversides. I think it's the strong smell.