The tank is 23.75" x 14.25" x 7" high. I used CaribSea "Eco-Complete" substrate, which is designed for planted tanks and comes soaked in fertilizer and good bacterias. I really like the natural look of the grains, but it was FILTHY to set up, clouding the tank for hours (hours!!!). In the past I used aquasolum black humate, which is a man-made product that looks like black BB's. It is clean, sinks fast, and the plants like it, but it doesn't look as "natural", which is what I wanted this time.
The plants are various Anubias with Staurogyne Repens as ground cover. The Betta loves the Anubias leaves. I have a Finnex Titanium Heater, Fluval "Planted Tank" LED (the programmable 3.0 version), AquaClear 20 filter, small sponge filter, and a 50 gph fountain pump at the far end. Originally I just had 2 sponge filters, which is all I ever used in smaller Betta tanks, but there just wasn't any flow in this low/wide tank and junk was gathering all over the bottom. Now with the HOB filter pushing along the front stretch, and the small pump pushing back the opposite way from the opposite corner, there's a gentle but constant circular current. There is one corner where the fish(es) have to actively swim, but 90% of the tank the Betta can stop and hover with his pectoral fins (the filter flow is on slowest setting).
I made a plexiglass lid to help prevent jumpers. I really don't like it, compared to a wide open top, but my last Betta (in a 3.5 gallon bowl) jumped out in the middle of the night after seeming totally chill for 6 months or so. He was a "common" betta from Wally-world (veil tail?). This new fish is a wild variety, so I didn't want to take the chance. I'm not happy with the placement of the feeding holes so I plan on making another soon. I'll wait till I'm sure of all the cords and airline placements.