My 20 gal tank which, until yesterday housed 3 two inch goldies, has a pH now of about 7.8. I raised it with crushed coral in a sack near the intake pipe on the filter.

When I do water changes, do I need to bring the new water's pH to that level with baking soda, or could this make the pH go even higher because of the coral? My tap's pH is 6.4.

Please lend a hand.

Hi,

The only thing I can think of is trial and error.

Either, try and get your new water to match with the tank's pH of 7.8 with soda. I don't know how hard or easy this will be.

Or, you could just add water to the tank without additives. The coral will bring up the pH by itself, but you may have a period of depressed pH. Not sure this is a good thing. It may not affect the tank pH because of the volume of water may be small, but I guess it would.

What I do is not aim for any particular pH, but aim for a KH of over 100 and see what pH I get from coral and baking soda. I add baking soda to every water change and am not overly worried about raising pH/dropping pH because KH is high.

Slugger

I think I would buffer the change water up in the mid 7s.
Here's a calculator you can use to figure how much baking soda to add.
http://dataguru.org/misc/aquarium/calKH.asp

Or you could let it sit with a water pump and crushed coral and let the coral raise it. Dunno how long that'd take or how practical it'd be.