Starting tank questions

[Mentat]

Hello, I have a lot of store credit at my local petstore, a 75% coupon thing and 60$ in credit, and am thinking of picking up some frogs while they are on sell. But before I do I wanted to do some basic research.
A. Will a 20 Gallon Tank be sufficient? I have a couple of 20 gallons and I have the skill to combine them into a sort of "apartment" style house.
Depends on frog species. Also, what are the actual dimensions of 20 gal.?

B. What is the best kind of frog/toad to get?
You might want to read this article and also look at what is available at store: Frog Forum - Choosing a Frog.

C. Can I house different species together if the size of the habitat is large enough?
What size is "large enough?" The usual answer is "no" due to differing parameter needs and toxic skin mucous that varies between species.

D. Can I keep fish with them?
Not usually. A couple members have kept guppies and similar with Red Belly Toads. Most frogs will eat fish or vice versa depending on who has the bigger mouth.

E. Are there any plants I can't keep with them?
Yes, you can keep live plants and will can read more about it in the Plant section.

Hello and welcome to FF ! Went ahead and answered your questions in the quoted section. Would help if you state your country and tell us your locality since many recommendations are affected by it.

[Tongue Flicker]

Also consider the type of terrain you want. Since you're asking if you could mix fish then mostly you have a fully aquatic frog in mind

[RandD]

I live in the US, in Florida. I was thinking of some dart frogs since I used to have some as a child. Is it possible to mix colors?

[Mentat]

Because of possible aggression, stress, and hybridizing; Dart species and even locality morphs should be kept with their own kind.