Ph Fluctuates drastically over 24 hours?

I have 25 gallon res that it seems some days, not all, but maybe once a week my ph will jump from say 5.65 to 7.50 in a 24 hour period. Any ideas? I am really at a loss.

Thanks,

What are the room/ res temps? Do you test consistently at the same time of day?

if this happens during a flush and or rez change then yes this is normall. it takes a good 24 hours to circulate that size rez if useing 1 on 5 off spray timer setting. no worrys, it happens to me.

BleedsGreen said:

I have 25 gallon res that it seems some days, not all, but maybe once a week my ph will jump from say 5.65 to 7.50 in a 24 hour period. Any ideas? I am really at a loss.

Thanks,

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Ph will climb like that when he plant drinks a lot of water but does not take in the nutes at the same time. Does your room get hot, like over 80F on occasion?