And inverts also need Ca
& other minerals in the water for maintenance of their shell. They do better in moderate hard water (say pH of high 7's). Depending on what your tap water is like, you might be better off using tap, or a mix of distilled & tap.
Another alternative is to add a remineralizing salt mix to distilled. That would take care of pH buffering and the Ca
the inverts needed. But this is more expensive than tap!
80 gal FW with 30 gal DIY wet/dry/sump.
9 fancy golds, 1 hillstream loaches, 1 rubber-lip pleco (C. thomasi), 3 SAEs, small school of white cloud minnows, planted.