Will the small container fit in a temperature stable aquarium? If so, you can float the container to get stable temp. Keeping it in a small container is good because you don't have to dose bigger treatments.
I have no idea if ramshorn snails are susceptible to Ellobiopsidae. My nerites weren't harmed by a bacterial infection my shrimp were suffering from, but I'm not so sure that's relevant.
What are you treating the shrimp with? I had a shrimp with Ellobiopsidae in a QT jar I was floating in my fish tank. I almost cured it by dosing the container with a few drops of hydrogen peroxide every week(a majority of the yellow/green had disappeared), but I took the jar out of the tank for a bit and the shrimp sadly died of temperature shock.