30C is too warm for just about any shrimp you can keep. If your water is getting above 75, it should be easy to cool any tank with a cheap fan.
Temperatures here were routinely 40C for several weeks in 2012 and I had no problem cooling tanks down.
Opae (Halocaridina rubra) could work. Ideally, you'd need to keep a specific gravity (salinity) of about 1.012.