I just bought a TDS tester from Amazon, and got it today. The tester showed store-bought distilled water at 000 TDS. The tap water in my building tests at between 045 and 049 ppm TDS. So that should be fine for carnivorous plants, right? I can stop buying heavy bottles of distilled water and forger about having to buy an expensive RO system? Of course, I'll continue to test.