A small one I started a few months ago, using some TEMU products. 2 x roughly 6 - 7 inches cubes and a usb LED light. Some TEMU's aquarium mini-products failed (the pumps, etc.)
Now, I have from Petco a blue male veiltail betta fish (about two have died prior) which survived our recent two week Eurotrip. And a neon tetra (had 4 before, all died out, along with some shrimps). I have a bendable moss in the betta tank. The other tank I used for filtration, so I will have more plants in that other one. Currently has two (from Petco): small Anubias Nana, Java Fern "Windelov".
So I currently run the two tanks on a timer for light and a mini water pump to circulate water between the tanks. I just bought a 50W water heater yesterday from Petco.