So I recently set up a 2.5 gallon I intend on using for Caridina. I'm going to be purchasing a tds meter and some salty shrimp when I get paid tomorrow. I'm planning on going super low tech, no filter and decently planted. My question is in regards to water top offs, as I don't plan on doing very frequent water changes.

When it comes to topping off the water, should I top of with just plain distilled water or should I top off with salty shrimp water? I lose what I would estimate to be 1/4 to 1/2 gallon weekly due to evaporation so I'd be topping off a relatively small amount. I'm a little confused because I feel if I'm doing top offs with plain distilled, the tds and gh will slowly drop but if I top off with salty shrimp water, the tds and gh would slowly raise. Maybe these amounts aren't enough to make a difference and I'm just over thinking?

If I should be topping off with salty shrimp water, can I premix a gallon jug and have the salty shrimp be fine sitting in the jug for multiple weeks? Being minerals, I'd assume it doesn't go bad or change at all in a sealed jug.