So, I have to ask...this tank is 4 feet long, 4 feet deep, and 15 inches tall? (L x W x H) Seems like an odd shape to me but I have never had a reef or fish tank....just curious.
We see large, square, shorter tanks like that a lot in reefing. It maximizes light penetration for light loving corals like Acropora, Millipora, and other SPS corals. It the same time it allows a lot of floor space to build your rockwork to display your corals on.
While it would be absolutely fine for Tincs, keep in mind that Tincs do best as a pair. That's a lot of viv for only 2 frogs. To me, that tank screams Phylobates or another group type terrestrial frog. Something like Bicolors, Terribilis, or Galactonotus could utilize the space better as you can put a larger group in rather than just a pair. Luecs could also be a nice choice but they will climb a bit more than others so they weren't my first choice.