Yeah that's what I wanted to do too, use the square for potting (it's a little deeper), but then thought it'd be better to utilize the whole space for plants, given how little it is already.
I will try my best the breed the rilis
they are culls though but from the pictures looked fairly blue. I want to see if more red striping returns in generation 1 (the blue + red looks amazing).
Are you using soil? If so, I sift the big pieces out, bake mine at 350F for 15mins, let cool. In addition to some gravel, put a layer of fine sand on so nothing escapes (also makes it easier to plant things so they stay). Shrimp are more sensitive to ammonia that may leech out, but should be okay if heavily planted. You also don't want air bubbles, I have maybe 2-3 Malaysian trumpet snails in mine aerating the substrate. Oh, and use DARK substrate so your shrimps' coloration are better.
Is your fiance into the hobby too? Lucky you can just send him out for stuff.