I am still thinking about a hillstream tank. I've never done one before so it's something new and I'm enjoying the research and kicking around ideas. The first thing I'm doing is trying to figure the best way to create a directional flow from one end of the tank to the other. Powerheads or a huge canister filter would be easiest. But I don't like the churning/tumbling current from a powerhead, and my tank stand can only hold a smallish canister filter. I'm reading up on something called "river tank manifolds." Looks like it would be fun to build one.
I envision this as a small stream flowing through a tea garden in Yunnan, southwest China. (Yes, I'm that nerdy about my biotopes) I want to have terrestrial plants--Chinese evergreen or similar, a clump or two of lucky bamboo, lots of mosses--growing up and out the top/back, with a waterfall coming out of the filter intake and down through their roots. Maybe a small fogger installed to add drama. I'm trying to decide if I want the hardscape to be simply a realistic creek aquascape, or more of an Iwagumi-ish, terrestrial-inspired scape. Either would look really nice. So would a combination of the two--terrestrial above and natural below--but that's a lot of visual effect to cram into a 30g tank.
As always, I'm thinking about stocking, because that's the fun part, isn't it?
Most of the species from this region are either unavailable, too big for my tank, or outrageously expensive. So I'm planning this as a "close enough biotope": Closely related, similar-looking fish that fill the same ecological niches and recreate the basic mood. I think that when the time comes I'll fill the tank with a small school of odessa barbs (to play the part of ticto and/or gold barbs), a dozen or so glowlight danios (standing in for assorted danio/devario species), a few Sewellia hillstream loaches (which actually do seem native to the area), and dwarf chain loaches (substituting for assorted botia and stone loaches) . Amano shrimp and snails, of course.