How large is your tank? And what percentage of the water needs changing?
If the tank isn't tiny, you may be able to hold off a few days until the water is back to normal. (One delayed water change isn't like keeping your fish in perpetually high ammonia and toxins.)
If your tank is small, or you think the water change really needs to be done, you may be able to get by with a partial water change, rather than a full one.
If you change out the water (any amount), I would use 'bottled DRINKING
water.' The label should say that it has dissolved salts or minerals. (It'll probably say something "minerals to improve taste.")
Do not use distilled water. It doesn't have the dissolved salts/minerals that tap water and drinking water have.
If you use the bottled drinking
water, acclimate SLOWLY. The water parameters (pH, dissolved salts, etc) may be different from what your fish is used to, and you don't want to shock him.
To acclimate SLOWLY:
- Note the temperature of the water.
- Using a plastic cup, scoop him, along with some of his water, into the cup.
- Clean out the tank. Refill with water at the SAME temp. Be sure to add the correct amount of water conditioner.
- Float his cup in the tank for about 15 min.
- Add a SMALL amount of NEW water to the cup. (Several tablespoons, or about 1.5 ounces.)
- Let his cup float for about 15 min, or longer. (It's always OK to wait longer.)
- Remove a SMALL amount of water from the cup. Discard it.
- Repeat steps 5-7, until at LEAST an hour has passed.
- Gently release him into the tank.
Then, when you go back to using tap water again, repeat the same slow acclimation process.