As long as you keep the water level to the point where they can't hop out you'll be fine, since this is temporary you don't have to fill all the way, send pictures! Use Bottled spring water or tapwater as of now if you can! Just make sure you dechlorinate if you use EITHER. I suggest a big bottle of Tetra Dechlorinater.
I use tetra aqua safe plus, here is a picture of it, I always keep it under the tank in the cabinet for my fire bellies, I bought the largest size which I think is a 9 oz? You're supposed to add it in when you do your monthly water changes.
I ordered it online from pet mountain for 17 bucks, This is a 16 OZ, though I've heard that beta conditioner works well too, so you could prob pick that up at any petstore for like 5 bucks.