Those are African dwarf frogs. A 10 gallon would be plenty of room for them. Also, about 4-5 years is a pretty normal lifespan for them.
Soft sand will be fine for the substrate. Don't waste your time with spring water, just dechlorinate your tap water. Actually, I just saw you said you have well water, so you wont even have to worry about chlorine
They'll probably eat every day or two and it obviously wouldn't hurt to do weekly WCs. If you just have the two of them in a 10, they could probably go more than a week between waterchanges though
Huh? Distinguish between ACFs and ADFs? It's extremely easy to distinguish between the two, ACFs are built like a tiny body-builder, where ADFs are proportioned like a skinny model. The difference is obvious...
most of the time they are labeled as dwarfs and are almost always ACF's. had mine 2 years now and he lives in my 125gal with an oscar, JD, red devil, and clown knife just to give you an idea of how big and aggressive they can actually get... she is the first one to eat and has been known to chase my red devil away if i throw blood worms or acichlid sticks in there. a 29 gal is fine for them tho be careful though and have ZERO gaps in your lid as they will jump out in a heartbeat!! and DO NOT throw little fish in their as they will be gone in the morning she is in the 125 because i woke up to find 2 of my 2" silvers dollars gone out of my 55 gal and my placket betta.
Since you said yes to the picture with a ADF not a ACF, then I assume you know what they actually look like.
Get a 10 gallon, use the same dechlorinator you would use for fish(I just use my Prime) and get some sand, and fill the tank up and wait a day so the bubbles will dissapear off the sides. Then put the frrogs in and your done. Feed every few days. Also get a few hides and some plants so they can hide if feel scared and so their not just sitting in an empty 10 gallon. Simple as that man, simple as that.