Thanks for your respose. I think blackworms are a good food but should not be used to often becouse they are a little bit fatter than other food. To keep them alive should be no problem. As you said they use to use air if there is not enouth oxygen in the water and they will breed if you feed them with salat, nettles or other organic material. But very slow becouse they take off their back and that have to grow to the origin size to be taken off again.
That you said about the water is no problem for me. Of couse there will be problems if you put blackwater (with mostly a lot of organic material) in a box and wait for a long time. The water parameter meight change a bit, but why do you want to filter that at that time.
Is it not clean enouth then you keep it?
I mean why do you want to have more than you use? Than there would be no problem.