When I need to add water, I try to do it out on the lake.
If I can't then I use the water filter that I have in my Kitchen.
I keep the aerator going, and keep the bucket out in the garage.
Try to get rid of the dead ones as quickly as you can.
I also add a some stuff that turns the water blue. It gets rid of the waste products in the water.
I think it is called better-bait.
Hope this helps,
Wiener