I’m experimenting with cultures that I can basically pour into the fish tank entirely, once “mature”. The culture I mean. For now I’m trying things in 0.5 glass jars at home on a shelve with moderate daylight. I’ve added tap water, a few Daphnia and small detritus worms that I scooped from a rainwater drum in my garden. On the bottom there are some specks of cocopeat and I fed the system a few times with dried yeast. So far, the Daphnia multiply, the worms too, the yeast seems to persist. Things go well. One jar had a solution with some drops of coffee creamer standing in it for a week before the water was replaced and the other animals were added. The cream had created a film on the glass in which the worms indulge. Next challenge: Massively increase the surface where the film can settle which hopefully increases the worm fraction. The nice thing about that is that I won’t pour the surface covered with film into the fish tanks with the feed. On the photo: few of the worms. If you magnify them a bit, you can see their chaetae.