I figure this is a good way to get the conversation going.
We currently have one community tank with a dwarf gourami, corydoras, neon tetras, a small colony of cherry shrimp, an assassin snail, and a plague of ramshorn snails that hitched a ride on some water lettuce we bought a few years ago.
I have multiple tank syndrom so I won’t go all out and just list of my most stable, somehow, tanks.
20 gallon long.
4 or 5 Upside-down catfish (Synodontis nigriventris, so freaking cool. Theit swim upside down)
5 to 6 Kuhli loaches, a few black and th other normal.
3 or 4 Yo-yo loaches. A whole herd of K Class Black Bar Endless.
A swarm of Amano Shrimp.
The most resilient Ramshorn snail colony I ever met.
Possibly 1 assassin snail. (Started with 4 before any loaches were in there. Thought they all died and found one randomly, can’t find it again.
If anyone is going to say it’s over crowded I know. Very much so. There’s lots of hiding spots, a few plants, and the water is stable. Somehow one of the most consistently stable tanks I have. All of my tanks are now doing great since I’ve been in the hobby a while now and have more experience. This tank was a "temporary tank while they adjust to the water and I’ll move them all to different tanks. Never had a death in there I know of since the assassin snails but to be fair I never found more than one empty assassin snail shell.