There are other appropriate fish choices beyond white cloud mountain minnows. Are you interested in a biotope?
Definitely not interested in a biotope, I have tried them, but I find them too restrictive. I'd prefer to just mix compatible species with proper conditions.
If you choose one of the Asian stream newts, you might consider keeping some of the Asian hillstream loaches with them. Their needs are similar, the loaches are inoffensive and keep algae down, and are not spiny (so you won't have newts dying if they decide to eat loaches).
I've kept hillstream loaches before, in particular a couple of species of 'Borneo Sucker,' that I was never able to identify the true species name of. They are neat little fish, and if there are newts that won't eat them, and have the same temperature requirements, that'd be great. My knowledge of newt-keeping though is anything but exhaustive, so I would greatly
appreciate it if you could pass on your knowledge of such animals.
Stream-dwelling plethodontids may be kept with various darters and dace.
I've never seen darters for sale anywhere in the city where I live, dace neither.
The only Dace that's native to my area is the Chub, and not only do they get huge, but they eat everything. Once I was fishing in midsummer, and was able to catch loads of these fish, so much in fact that I ran out of worms. I started fishing with bare hooks, and was still able to catch them, in fact I caught the same one on three different occasions, once with a worm and twice with bare hook. These fish are profoundly stupid, and with an appetite so great that they'd try to eat a bare hook, I don't think I'd like to mix it with a newt.
A tank as you've described, depending upon the speed of the "stream" would work well for Taricha species, in particular rivularis, though I can't recall at the moment, ever seeing rivularis in the pet trade.
In fact, I did try to build a very similar style tank (55 gallon) for my granulosa, but unfortunately I could not get the water to stop leaking into the land area, no matter how much darn sealant I added. I know the pictures are on this website somewhere. I'll add the link if I find them.
Would the granulosa be fish safe?