Most shrimp that are sold for a fresh water tank are algae eaters. Cherry shrimp, Ghost shrimp, and Amano shrimp will all be fine just eating algae. BUT there may be too much algae for your tiny shrimp to eat it all up.
There are shrimp foods available, if you think they are not getting enough to eat.
I disagree about ghost shrimp, they tend to be more carnivorous than simply algae. At least that’s how mine were. my red cherry shrimp on the other hand have never been fed except for algae and biofilm that is in my tank, and I have had a thriving colony for about 4 months now that constantly is growing
I suppose that's possible. I never had any trouble with my ghost shrimp, but that may well have been because they were taking advantage of left overs from fish feeding time.
I have a bad habit of assuming that there are fish in every tank. If this tank is only shrimp, some supplementing is probably a good idea.
I would. I've seen my amanos eating cherry shrimp if I don't feed them. No proof that the cherry shrimp wasn't already dead, but the amanos are very aggressive when hungry. Algae wafers or shrimp pellets every couple days should suffice