PH going down ??


Prolific Poster
Oct 17, 2007
South Florida
Tank 11 months old and well established. Had an unexplainable PH swing down to 5.0, 2 fish died. Don't suspect my CO2 injection.
The chemicals:
Had-A-Snail dosed correctly.
Excel, dosed correctly and long time use.
Flourish dosed correctly.
Flourish Trace dosed correctly.
Plantex CSM 1.5 gram at water change only.

Last 3 (weekly) water changes have been only 25% instead of the customary 50%.

Another odd thing: KH test kit (API) first drop does not turn water blue,
second drop turns water slightly yellow. KH 2?
Tap water which I use does turn blue and then yellow
for a definite 2dKH

-Have done 50% water change and KH testing still not blue at first drop.
but tap water test is good at 2dKH.
-PH after water change 7.0, turned the CO2 steel cylinder valve off, overnight, and
this morning PH is 6.2.

What can be lowering PH?


Lifetime Charter Member
Lifetime Member
Jan 24, 2005
Sacramento, CA
If you use a drop checker with 4 dKH distilled or deionized water in it, you can see if your CO2 concentration remains within limits. Otherwise you can guess or assume that it is ok. Don't use chemicals to get rid of snails. If they are getting more numerous you are very likely over feeding the fish. Snails only have population explosions when there is excess food available for them. I don't know that Had a Snail will lower the pH, but it might.