Any special considerations when moving Trapdoors to a new tank?

I recently got 3 Giant Trapdoor snails from snailshop & they're amazing & appear to be breeding already!

Anyway, I'm in the process of setting up a brand new 240L coldwater tank for fantails. The snails are currently in a mature, established 90L tank & have loads to munch on to keep them happy.

I'm just a bit concerned that there will be little if any food in the new tank when it's ready. It's brand new so there's no algae or dead plant matter for them.

What can I do to make them comfortable in their new home? What foods can I put in the tank for them that the fish won't eat?

Many thanks