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I have just tested my tanks and the readings are as follows:-

1st tank: 7.2 PH
GH 197ppm
KH - 3

2nd tank PH 6.4
GH 197ppm
KH 3

Zebra tank: PH 7.6
GH 237ppm
KH 3

I can't understand why there is such a difference in PH and, I would like help in understanding the difference in GH and should I be worried about the low KH of 3 in all tanks. I, obviously, don't want to experience a PH crash in any of the tanks.

Thanks
Jenny

Well I have been told that there are certain types of rock decor that could make your ph go up, and I think putting driftwood in your tank bring the ph down...I am not completely sure how it goes...but maybe it's some decor that youi might have in your tank