What causes pH increase?

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fgump

AC Members
May 17, 2007
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Utah
I went on vacation for a week. When I came back, my pH was 0.2 higher than normal. I'm not concerned about 0.2 increase, mainly wondering what would cause the pH to raise. And I will gradually lower it with my normal water changes - hopefully anyway, unless there's a bigger problem going on than I think.

My aquarium is only about 3 months old. And my aquarium water has always been 7.8, which is the pH of my tap water. The only things I add to the water are Prime and fish food.

And since I know it's going to be asked, my water params are:
Ammonia: 0
Nitrites: 0
Nitrates: ~10
pH: currently 8.0, but is normally 7.8

I have a 29 gallon bow front tank. Current inhabitants are 5 trili cories, 1 black molly, and 1 apple snail that's about 1/2 inches (maybe slightly larger). The tank has no live plants.
 

fgump

AC Members
May 17, 2007
254
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Utah
Only thing in my tank is plastic. Only fake plants (for now), and no real rocks. Just plastic stuff I bought at PetsMart. And the substrate is the standard aquarium gravel you get at PetsMart also, no sea shells or coral in it. I do have a piece of driftwood soaking that will go in this weekend. But it's not in yet.

The charcoal in my filter has been in for about a month, but I doubt that could cause it.
 

ct-death

Fish & Visitors Smell in 3 Days...
Feb 27, 2007
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New Hampshire
TDS can slightly increase ones pH. Obviously not all dissolved solids will have a direct impact, but many do. Over time a tank's pH will rise slightly if not maintained.

I help out at a LFS and she has UGFs in all of her tanks. Every 3 weeks she tests for pH ONLY. Usually after 6 weeks her pH goes from 7.6 to 7.9 and she changes the water using this as a guide :shrug: Now that's only 0.3 change over 6 weeks.

Just throwing that out there ;)
 

PiQ

Registered Member
Jul 21, 2007
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Not sure if this is helpful.

The straight forward answer is the fishes caused the pH to increase.

The fish excrete their nitrogen metabolic waste into their surrounding as ammonia. The ammonia is a base, or alkaline if you prefer. The pH of the tank will increase if you add base to it.
 

PiQ

Registered Member
Jul 21, 2007
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0
Oh, I never consider the conversion to nitrate. As you can see I'm new to this aquarium business.

This might be little bit off topic.

But if all the ammonia are converted to nitrate shouldn't the pH return to the original level, not lowering it?
Nitrate and nitric acid are two different species. There is no hydrogen on the nitrate molecules to deprotonated, therefore it shouldn't lower the pH when the bacteria convert the ammonia to nitrate.

Please let me know if I'm wrong in my reasoning. Thanks!
 

silentskream

AC Members
May 16, 2004
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Florida
uncycled ammonia will increase the PH, yes.. but according to the measurements indicated at the beginning of this thread, there is no ammonia. it has ALL been cycled.. soo it probably isn't the cause.

you aught to check the hardness of your water.. extremely soft water will sometimes change ph quickly.

how were the fish taken care of while you were away? did you have vacation feeders? automatic feeders? a friend come check on them? or did they just tough it out for the week?
 
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