what will eat decaying leaves?

ALMOST any snail will. Ramshorn, Bladder, Any Apple Snail, MTS, Q. Mels, etc...etc...etc....

some snails will but i dont really recommend that. decaying leaves will mess with your water parameters, it is best to manually remove dead/decaying leaves.

Yes squirrel the above listed snails are pretty safe with healthy plants just clean up the decaying ones but you must remember that the snail then in return needs to be fed properly or will start eating healthy plants.

You can feed stuff like algae waffers that sink to the bottom or snail jello, mainly you need to give us an idea of what kind of fishies you got in there that will compete for the food.

There is a sticky for snail jello recipes on the invert forum. (fish will eat this too- my Cories esp. love the stuff)

I keep a zucchini slice in my aquarium. Originally for the pleco- but now I have a brig snail, it's for the brig too (and he eats a lot of it). It's usually covered in Ramshorn snails too... occassionally a ghost shrimp or a Corydora will graze on the zucchini. Strangely the bladder snails and MTS rarely touch the zucchini. It's the brig and ramshorns that eat it.

Good thing is- it's fine in the tank for a couple days (although now I have the brig it doesn't last that long) and doesn't get eaten all at once- so the snails always get to have a share.

You can also mix fish food into plaster of paris pucks... plaster of paris helps provide your snails with calcium- and because it lasts a while- you know the fish won't hog all the food in it and the snails can get some.

The snails no doubt that I have are getting their share of fallen fish food and various sinking foods I put in for them, the shrimp and the Corys.