My office is slowly becoming a place where nano tanks are being shoved everywhere. I love low tech
Smallest is a 1g jar for my scud culture. These guys are fantastic and soooo easy to keep. I have a small random piece of driftwood, some cholla wood, lots of moss, salvinia, and random other plants that were either dying or became covered in algae. The scuds clean the algae and eat any dead leaves/plants leaving the healthy alone. I rarely feed them and have the yarn in the tank to be able to feed them to my betta. There is a sponge filter with a very slow bubble in there too.
My Betta, Ollie, is living in an experimental 3.5. I started this tank with trimmings from other tanks so I'm still waiting for it to grow in. He is very happy and loves hunting the scuds I give him once a week. I think I HATE the white sand and will NEVER use it again.
The biggest nano I have right now is my 5.5. This is filled with plants that are growing like crazy. I've got H. Formosa, Blue Velvet shrimp, MTS, ramshorn snails, and a few scuds weren't eaten so they are trying to start a colony. The H. Formosa are keeping their numbers way down though. I feed this tank once a week or so. Everyone is thriving and I found my first H. Formosa fry today! I have a super red bristlenose pleco juvie in here until my 29g is cycled and ready for him/her. Its AMAZING what a 1.5" pleco can accomplish in just 2 days. The glass looks amazing. My moss walls are growing in and the roots from the water lettuce give the fry plenty of places to hide.