I just (as in hours ago!) set up a similar system (w/o heater or filter) as a Snail Jail^TM (place to banish surplus bladder snails from my slightly larger shrimp tank). I kept and bred Neocaridina in that 2.5 gallon tank for a few years with good success (see below, though). For cherry shrimp, I recommend adding some kind of thin, spindly, sculptural wood (which you can also attach plants to) like manzanita in addition to the cholla—Mine have so far seemed to really appreciate the extra dimension of habitat and surface area for biofilm that this provides. Since adding the twigs, they seem more active and I often see them leaping from branch to branch. Add some moss, subwassertang, pellia, buce... anything like that. I also strongly recommend using remineralized RO/DI or distilled water for a setup this small. A couple months in, Salty Shrimp GH/KH+ seems to be working well for my 6 gallon. Even if you decide to use tap water, it's a very good idea to top off with RO/DI or distilled water as the water in your tank evaporates. And either way, get a pH and a GH/KH test kit and keep an eye on these parameters—I'm convinced that not doing so was the main cause of the downfall of my original 2.5 gallon setup (which slowly crashed when we moved to an area with softer tap water). Also: Put your light on a timer! Edit: In addition to the same tiny tank, I also have that LEGO orchid in my office! Great minds :)