PH problem

[karrihug]

i just cycled my 56 gal tank. didn't test ph till almost the end cause i figured it would be the same as the others filled from teh same tap. mine stays right at 7 normally. the new one was at 6(or below). did an 80% water change as soon as the nitrite fell and it was then at PH 6.8. in 2 days it fell back to 6. i thought it was something to do with the cycle so i added a tiny bit of baking soda to bring it back up to 7 so it would match the other tanks, praying this would work. 3 days later and it was at 7 tonight. so far so good. but then i decided to test my daughters tank and it was at 6, we just changed almost 60% of the water sat and again mon because food had been spilled in the tank and it had to be cleaned up. so we tested the tap water in the kitchen adn it was at 6.8 same as the last time, waited a few minutes(i was pondering) so checked it with dechlorinator thinking it was making it drop, it was off the charts, over 8. went to the bathroom tap and got the same reading, bathroom with dechlor was even darker blue. dont know what to do, or why it is acting like this. has anyone ever heard of this?

please help
karri

 

[semper fi]

you could try to add some crushed coral to stabilize the ph. what type of substrate doyou have in the atnk? what type of media are you using?

 

[karrihug]

substrate is very small river rock, and the filters are penguins with biowheels and the standard filter cartridges. i have a piece of bogwood in the big tank and thought that might be causeing it there but my daughters doesn't have any. i am worried about water changes actually making it swing wildly now. do you think the water company could tell me anything?