I never use soap to clean my tank or toad accessories (ceramic cave and bridge) but a few days ago I noticed a lot of little bubbles/foam gathering on object in the water, including my toad. I have a waterfall-style filter and I just added some new rocks to the tank so I thought that maybe that combination was churning up foam so I moved the rocks away from the waterfall and changed out the water with distilled water from the supermarket just in case. The next day I bought some water test strips to test the new water and, to my surprise, it was acidic, not neutral. I've tested it a few times, even pouring some of the water straight from the jug onto a test strip. My toad seems perfectly happy to swim in this water and I can't understand why distilled water would be acidic right out of the bottle. Is it going to harm him?

Tl; dr: What to toads need for good water?