I used to raise snails, intentionally, and I learned a little trick that might help those that try to breed and feed tadpoles.

I grew a LOT of algae that covers various surfaces from rocks to tiles and broken raw ceramic to feed to my snails. It was quite easy and the snails loved it.

Here is what I did:

In a small glass aquarium, I put in the growing surfaces for the algae. I used a lot of broken ceramics because it is so porous and the algae grew very well on it. It also clung to it when I moved it where a lot of times it would slip off smooth rocks and other surfaces. I added various nutrients for aquarium plants in small amounts for a food source. Then I set the container in a bright window and left if for a couple weeks until the water was as green as it could be. I also did use Miracle grow once in a while at a very dilute ratio, mixed at 1/8 recommended ratio. I do not know if I would recommend using it with frogs but the snails never seemed to be harmed by it. I read that by the time you are ready to feed the algae to whatever all the nutrients have been consumed by the algae.

I do recommend that you stick with the standard aquarium nutrients just to be safe since I suspect that some if not most frogs might be a little more susceptible to Miracle Grow and some of it's contents. I simply used a micro nutrient with small amount of macro nutrients and let the algae eat it all up. Then my snails ate all the algae.

Here is where I got the fertilizers: Planted Aquarium Fertilizer - , , , , Planted Aquarium Fertilizer - , ,

And for your first attempt, find some algae in an aquarium or vivarium and seed the growing tank so you have a clean source.

I used to have a coupe really good articles in intentionally growing algae but it has been a long time ago and I lost them. Will post them if I find them again.