Frog should be bred with spider eyes.

In the current 1.19 snapshots and betas, frogs are bred with slimeballs. From a real world perspective, this doesn't make a whole lot of sense. 

Frogs are insectivores, meaning the eat small arthropods. Having frogs eat spider eyes would better remember their real world diet. 

From a gameplay sense, spider eyes are quite a niche item and have very limited uses. It's one of those items that you gather stacks upon stacks of, but never use. Compare this to the slimeball, which is one of the most useful items in the game. 

The slimeball doesn't need another use, but the spider eye definitely does. Making it the food item for frogs gives the spider eye much more use, and better matches the real world diet of frogs.