Okay, I actually did the 2.5G with a piece of black polished granite floor tile. Lowes cut it to 7 1/2" by 11 3/4" (both cuts free on their wetsaw), and it fitted perfectly into the back, using some aquarium silicone to hold it in place. (Left it alone for 48 hours, lying on a towel on a shelf; this gave the silicone seal time to cure, and allowed the weight of the granite itself to assist the 'clamping'.)
Substrate chosen was Tahitian Moon Sand. I rinsed...and rinsed...and rinsed some more...and ended up with a two-inch substrate of purty black sand.
I planted glosso. Ugh. What a pain. One doggoned plantlet at a time, with 10-inch tweezers I got on eBay. But it'll be worth it when it grows in.
I've got a DIY CO2 setup with an airstone bubbling straight into the intake of an AZOO Palm filter that I'd already seeded for several weeks in an established tank. Water was a gallon from the same tank, and the rest is dechlored tap water. (Unfortunately, the blue tubing from the CO2 rig is REAL visible, at this point-I'll do something different later to better disguise that part.) Lighting is a Coralife Aqualite 18W freshwater fixture, directly on top of the plexi top I cut.
In the center I have a monolithic piece of bogwood,with a java fern plantlet and some java moss (I intend to add an anubias nana petite...ummm...when I can find or am gifted with one...). Behind the bogwood is a clump of fanwort. The bright greens of the plants are a great counterpoint to the black background and sand and the dark wood.
Denizens at the moment are about a dozen h. formosas. I'm going to add some cherry shrimp later if the batch I bought don't die off (they're all in hiding in another tank).
So...without further adieu...:
Commentary is, as always, welcome. Personally, I'm happy with it...it's what I envisioned when I started out on this one. I'm thinking that after the glosso grows in well, I'll take this tank to work, bring the hex home, and redo it...got a couple ideas...