ok....

1. large rocks as a substrate is a no-no. ACF can accidentally kick these as they go to kick off to swim, and a loose one can be sent into the glass with enough force that the glass can crack.

2. bloodworms - - should NOT be used as a main part of the diet. they have very little nutritional value and would be like a person living off of cream puffs - very yummy, but not healthy! also brineshrimp is not something larger frogs will take great joy in eating due to how small the pieces are.
your best bet for a balanced diet are the floating Repto-Min sticks you find in the turtle section. these are very nutritional and will be a wonderful rich diet for the frog.

3. as far as having more room for additional frogs - - it is a 20 gallon correct? in a 20 gallon standard or tall tank, two frogs is it. in a 20 gallon LONG tank you can have three. The reason you can have more in the same volume is surface area - the long tank gives the frogs much more room to move around.