That didn’t really answer the blackworm question, I think what I meant was that they are easily available in pretty large quantity from stores, so I only worried about keeping them alive. For a live food from a store it is actually a lot of food for the price, compared to other live foods. But they may not be available everywhere.
Putting a filter with peat in a 5 gallon container, this would work just as well as the drip method I think, but I wonder if it reaches a certain pH and then further filtering makes no difference, or if there is a certain time limit of filtering that you should follow.
Also wonder if it is possible to premix water and let it sit or if it will change over time.