Hi,
I prefer sand over gravel in frog tanks because food can´t sink in and the frogs can poop out some sand corns if they accidentally devour them (that´s not possible with fine gravel).
ADFs are best fed with a variety of small enough wet frozen or live food items, such as brine shrimps, black mosquito larvae, glassworms, daphnia, enchytraea, tubifex, mysis, chopped earthworms, bloodworms etc. I don´t recommend to feed exclusively on bloodworms, because they don´t contain all the nutrients a frog needs to stay healthy and they seem to promote dropsy if given in large amounts. If your frog isn´t used to frozen food, it may take some time until it recognizes it as food. In that case, you would need to remove uneaten leftovers after about an hour to keep the water clean, but the frog will eventually learn to eat it

Is there only one frog in the 30 gal. or is this a community tank? Fish usually are much more greedy when it´s feeding time, so you would have to make sure that the frog gets enough food. Also, ADFs are rather sociable animals, so maybe you would like to consider adopting some more conspecifics.