I have had a tank for 2 years now. Thanks to some bad advice from the lfs, it has been an experiment in "which fish can survive".
I have a 20gal hexagonal tank (looks pretty, but not as useful as a regular tank). Filtration is from a hagen/fluval 205 canister (110 gph) and a marineland//penguin biowheel 200 (200 gph), so the tank is vastly over filtered (about 1x every 4 minutes). One big ol bubble disk powered by whisper 40.
Plastic planted aquarium, with quite a bit of java moss wrapped around the plastic plants. Provides pretty good hidey holes for the aquatic wildlife. I used to have a stone gravel base, (1" to 2" pebbles) but the food would get into the crannies and the cories could not reach it. So, I switched to a Tahitian Black Moon sand. Everyone's soft parts seem to be fine on this substrate.
5 blue tetras (bad idea, they are territorial in my small tank)
5 neon tetras
6 white cloud minnows
2 cory catfish
2 yellow apple snails (female)
1 blue apple snail (male)
1 brown mystery snail (probably male, growing much slower than the others)
25 +/- ghost shrimp
Since the tank is overstocked, I have to do a lot of water changes to keep the nitrate in check. But the fish seem happy, and the levels are pretty good. Usual water test results:
ph = 8.4+
total alkalinity (KH ppm) = 300+
total chlorine ppm = 0
Total Hardness (GH ppm) = 300+
Nitrite (NO-2 ppm) = 0
Nitrate (NO+3 ppm) = 20 to 40 (over 20 leads to a 10% water change)
can you guess that I use the quick dip tests
Water is really unsuitable for the tetras (I think they like hard water), but they have been healthy for 2 years, so I don't think it is too bad. My snails are really happy, and constantly mating, which makes me giggle. I have a video of this on youtube: http://www.youtube.com/watch?v=HWNXCmp7Gjw
Anyway, now I'm trying to figure out better tricks & techniques, and if I know anything (unlikely) I'd be happy to chime in.