Daphnia is a frozen food for fish, water fleas or water bugs. I would stay out of live foods.
And fish should be fed variety of foods, from commercial to frozen or freeze dried and since you got guppys in i would recommend you to offer them couple veggies per week and algae wafers to ☺
i like to use hikaris algae wafers.
I give them flakes & the bottom feeders have their own food, although the fish seem to prefer that, while the bottom feeders seem to prefer the flakes, lol. They also get bloodworms sometimes. The little granule food is for the fry.
I tried algae wafers before, & even the algae eater showed no interest. It doesn't eat the algae in the tank, either.
Which is why I want snails. They do great in the 10g.