I never trusted chemical de-chlorinators, and I never trusted the "leave tap water out overnight and the chlorine will evaporate" advice. With distilled water you've got the ideal environment for freshwater fish. Just their presence in the water will start to add electrolytes and make it a more natural water for them.

Pros: No chlorine, guaranteed

Cons: The cost, but your fish are worth it

Luckily we have well water so adding water to our pond is not a problem. Just need to test it occassionally for excessive bacteria. Keep a gallon on hand to use in the iron.

Pros: No chemicals

Cons: price

We use distilled water to mix the salt into when we do the water changes. It is easier to get it right with no other chemicals.

Pros: perfectly neutral

Cons: expense

I have used distilled water int he past. I find it works okay. I prefer to use my home water

Pros: okay

Cons: none