# How much of a daily pH swing is okay for fish?



## Ming shipwreck (Feb 26, 2011)

Hi all. I was wondering how much of a daily pH swing people have in their planted tanks, and how much you think fish can handle. I have a low-tech, heavily planted, stocked tank (white clouds, guppies, 2 crayfish) that gets a lot of sunlight. My water is rock-hard, I think around 10-15dK (the strips are hard to read precisely). My daily pH swing is around .5, from 7.7 in the morning to 8.2 in the afternoon. I consulted some tables for estimating CO2 level, the CO2 levels fluctuate somewhere between .2 and .8 PPM, so within normal range for outdoor ponds. No signs of oxygen deprivation, but some of the white clouds especially have gotten sick, and there has been an outbreak of something that might be velvet, the fish have started flashing a lot, but I notice this is much, much worse in the afternoon and evening, so I'm thinking it might be related to the high pH at those times. Or maybe the pH swings are just weakening the fish.


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## jrman83 (Jul 9, 2010)

If the swing is the natural swing in a planted tank where the plants use/give off CO2, I don't think you have anything to worry about. It is a natural swing. My ph swings daily within a full point going from when my pressurized CO2 comes on until just before it shuts off and my fish are not affected by it.


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## beaslbob (May 29, 2009)

I think you fish are fine.


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