How to safely do a water change with water of a different ph?

[princessearrings]

Hi! My tank is fully cycled and it's ph stays steady at 8.2. I have to do my first water change with fish in my tank. I can't use my tap water because it has ammonia in it, so I bought spring water (hope thats okay to use?). The ph of my tap water is 7.6 after I let it sit for a couple days. I tested the spring water and everything was fine, except the ph. The ph of the spring water is at 6.4! How should I do a water change without the ph fluctuating too drastically?
Thank you!

 

[Bderick67]

Do small 10% change and see what that does to the tanks pH. You may not see much of a change. Then gradually increase the amount of WC always watching how it affects the tanks water params.

Why does you tap have ammonia, is it chloramine? What level ammonia is the tap. If low you can still use it as long as you treat with prime. You can do small % WCs and then watch your params, you'll find that the ammonia disappear within a few hours.

 

[Toby_H]

Either do small water changes...

or buffer the spring water prior to using it...

It's likely the GH, KH, etc of the spring water is different from your tap so small water changes makes the most sense...

 

[squint]

You could use chemicals to neutralize the ammonia or, if it's just ammonia and there's no chlorine or chloramine, run a biofilter for a few days in a storage container to remove the ammonia.

I always assume my water parameters are different and just add the replacement water very slowly so the fish have time to adapt.