Your tank looks great!
I have the 12-gallon, too, with lots of plants. I was able to cycle my tank in about 2 weeks using two different bottled bacteria solutions and placing some of the rockwool in my filter from some plants I bought to help seed the tank. I have no idea which of the three (one of the solutions or the seeding material) helped the most, or if it was a combination.
I have a betta in mine with 9 cardinal tetras, 1 cory, 1 pleco (tiny/dwarf), nerite and apple snails, and, just recently, some amano and cherry shrimp. It's a very active tank. My amonia and nitrites are at zero, and my nitrates are around 20, so it doesn't seem to be overstocked, but I'm keeping a close eye on it to make sure. I'm sure I'm at the upper limit of the bio-load for this tank. I do partial water changes every week, and I think the plants help, too. It's like a jungle in there with my new aponogeton ("wonder bulbs"). I'll probably have to prune them back soon. I also have Amazon sword plants, java moss, and some others.
Anyway, just wanted to chime in about the stocking ideas and let you know what I have in my Fluval that seems to be successful so far.
Here's a pic of mine.
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