I got a new female yesterday and set her up in a 1.5g (no heater or filter, but frequent water changes and a very warm bathroom--it's a quarantine--don't eat me). My husband recently boiled some small pieces of driftwood, so I put one in her tank as a place to hide.
This morning the water looked like tea from all the tannins! I guess he didn't boil it long enough! I measured the pH and it was 6.7, down from 7.8 the previous day. I did a water change but only half, and added the fresh water very slowly, and removed the driftwood. She is showing stress lines, but she was showing them when I brought her home last night. Also she is feisty and eating.
Should I be worried? All the info I can find says "don't subject fish to sudden changes in pH or drastic fluctuations" which is very vague. How big is a drastic change? Should I just do many small water changes to readjust her?