[Jacob]

Thanks for the responses, good to know the pH is not likely to crash.
The R/O water I would use is sold in fish stores for people topping off saltwater tanks, I will learn what the values of it are. I liked the idea of adding blackwater extract just because it seems like you could have a formula that you repeat every time for exactly the same water. I will have to filter the r/o water, and I assume it usually ends up in the same range and there’s an amount of difference that can be tolerated safely. I wonder if cryptocoryne could be used, since they are amphibious. Pitcher plants or other interesting land plants would make a good display and it could be a biotope of where the fish come from, but I don’t know if those bog plants affect the water too much. Combining plants and weak filtration seem like a good idea.
For blackworms, they’re easily bought in stores where I am. I never tried to breed them, but they would always multiply in the gravel. This was a good thing for the dwarf puffers I was keeping since they would catch them throughout the day. But some don’t like worms in their tank. Over time they are supposed to get smaller and weaker in tanks, because of oxygen being less in the water column than if they could use the air (if I rememmber right.) Stores keep them in shallow water in refridgerators, so their metabolism slows down and they don’t need to be fed, I think.
They would die if the tank I kept them in had no aeration. They would eat pieces of brown grocery bag paper, and almost anything else. Keeping them in shallow water or keeping them submerged in water clean and aerated seemed the most important requirement for keeping them alive, I don’t know about breeding them.