I have just built/rescaped a little standard 2ft (50 odd L) aquarium for my two little hillstream loaches.
I hope that they enjoy it, they aren't in there yet, waiting for a bit more algae growth.
I has more flow than my small torrent fish tank, that has about 500l/h flow in another 2ft tank. This new setup has a +3000l/h pond pump turning over the water. This really pushes the water around, and small rocks/gravel.
It still needs a few more rocks that I'll grab either one evening or on the weekend from a localish stream.
Watch id HD to see the flow of bubbles: