PH in my water

So measured the PH in my water last nyt for the first time in a while and it was 7.6 so put in the correct amount 2 bring it down a little according 2 the instructions on the box and I measured it this morning and it was about 6.6 at this point I was quite worried at such a big leap between numbers as according 2 the box it should have only went down about 0.1 or 0.2 so I left it for a while as I didint want to mess about wif it any more as the fish don't seem 2 be active at all apart from my corys so when i got in 2nyt at about 23:00 I measured it again and it's back to 7.5, i don't really have a clue wars goin on to be honest and don't fink the fish do ether

why do you want to bring it down? are the fish all happy and healthy, if yes then just leave it be IMO.

If you do want to bring it down then the only really safe way to do it is to take stuff out of the water, not put stuff in. The reason the pH is so high is cos of all the salts and carbonates etc in the water. adding more stuff in is only going to cause more issuse. Seriously, unless you are going to filter the water and remove some of the bases then dont much around with it.

You can buy water filters these days for very little. Even a 2 stage filter will help remove some of the stuff in the water. My tap water comes out the tap at 8 but goes up to about 8.3 once the CO2 come out. Using a 2 stage filter it comes down to about 7.5, using a 4 stage RO unit it comes down to 6.2

pH modifing chemicals are nothing but a sure-fire way of stressing out your fish and will bend your mind when it comes to crazy swings they cause!

I agree with Doug it's far better to leave the pH it as it is rather than have constant swings.

Is the pH of the water you are using for water changes at high, if not there could be something in your tank causing the pH to rise.

.

Thanks 4 your advice guys yea the fish seem healthy just a few havint really been active 4a few weeks and I was thinking maybe that had somthing 2 do wif ph. The water I use for changes is low ph so that's y I'm confused!

There are severa reasons why tap water will have a lower pH than your tank's water. The first reason is that tap water has a lot of carbon dioxide disolved in it which lowers the pH. This will come out of solution slowly over the first 24 hours or so. To check this put some pat water into a bucket with an airstone and let it bubble away for 24 hours then retest the pH. I can promise you it would have gone up. Mine goes up from 7.5 to nearly 8 and considering pH is a Log scale that is a big increase.

The second thing is things in your tank buffering the water to a higher pH. First things to look at are your substrate and any rocks you have in there. If they contain carbonates then you have found your reason. Then check your filter media, some filter media is designed for marine or african rift lake tanks and buffers the pH higher. 9/10 times it is your substrate though

Totally agree with Doug and Kfenk.

In addition, you must be very careful, cos pH-shock could easily kill all swimming creatures in your tank.
Remember, pH is logarithmic and as a result, pH 6.6 is ten times more acidic then pH 7.6. You are damn lucky that your fishes are still among the living.