Brrrrrrr!
I would get an adjustable heater and keep it at a low setting just to assure itCongrats on the beautiful shrimp.
Make sure you feed them a food which has astaxanthin, I will feed some sprinkles of Seaweed Extreme by Hikari for them. But what seemed to really get the shrimp happy was using some frozen food. For small number of shrimp you can slice off a tiny part of a cube. One which I really like is Cobalt Coral Food frozen in little cubes.
Also sometimes the shrimp are fed a color enhancing diet.
There are many kinds of foods available specifically for shrimp. Online a few sellers have a combo pack of a number of foods in sample sizes.
Leaf litter, like small or cut pieces of Indian Almond Leaf, Mulberry, Guava, Oak, Alder cones, etc. Cholla wood, all encourage microscopic foods to grow on them some called Aufwuchs.
As for the foods feed lightly thinking size of the eye of the shrimp as how much pellet or prepared food it needs per serving/day, with other foods like the leaves and mosses to graze on then you will not worry of over feeding. If you see saddled females then maybe increase food an extra tiny serving. Frozen foods help.
As for Bacter AE I have been using it but hard to say what it does. Just does sparingly. I haven't been using it as much as it says. Also if I use the Bacter AE, I won't really feed for that time, like as dinner uses Bacter AE no food, next day maybe a light meal. Then maybe that next night a regular amount serving.
For a clean up crew, I have a few MTS and some Red Ramshorn snails to help clean up any left overs. The big size/full grown Mystery snails I don't keep in a shrimp tank, maybe a baby size to marble, because if one full size dies in a nano tank it can ammonia kill the shrimp.
I also use the Snow food which seems to be soybean hulls. Again won't feed on that evening, like with Bacter AE.