Shrimp are scavengers, they'll eat whatever they can find, they don't need special foods...in a biologically mature tank, they'll be fine
How long has the tank been set up?
I use them for filling vials like you did, but rarely test my water any more
My main use for them now is dosing water conditioner...much more precise than the "capfuls", which is often recommended
How about a FTS* of this tank?
I'd like to see how you have it set up, being temporary and all, and very small, for breeding purposes....deco?...plants?...filtration equipment?
Again, congrats... @GaryE will be an excellent source of info with these fish, you're fortunate, in more ways than...