Concerned about pH rise

30king

Junior Poster
Jun 15, 2008
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Rocklin, CA
Hi Folks,

I have a relatively new 90gal setup. I'm using pressurized CO2 with and inline reactor from my sump, controlled with a pH controller. I shut off the CO2 at night using a timer. I'm also titrating up EI ferts. based on my bio load. My substrate is 3/4 flourish and 1/4 coarse playground sand.

My question: Using my pH controller, I've noticed over the course of a few weeks my pH climb in the tank from 7.6 out of the tap, to 7.9 at night after the CO2 shuts down. My GH and Kh was 1, and this pH issue occurred prior to me raising both to ~3. I'm concerned about this nighttime pH because I want to put cardinals and angels in the tank, and feel this pH is a little high.

I'm a little reluctant to chemically lower my pH. I was hoping to get some perspectives from anyone about this. ie.. result of ferts, result of press CO2, any solutions, etc.

Also, is the addition of Bicarb and GH booster going to automatically raise my pH? My tap water is soft-GH/Kh 1 and pH 7.6, so I'm a little confused on the chemistry.

Thanks
Adam
 

VaughnH

Lifetime Charter Member
Lifetime Member
Jan 24, 2005
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Sacramento, CA
Raising the KH will raise the pH too. So, adding sodium bicarbonate (baking soda) will raise both the KH and pH. Why are you raising the KH? You do need some calcium and magnesium for the plants, so raising the GH can be beneficial, but I don't see a good justification for raising the KH.

In any case, the pH swings that occur as you add and not add CO2 to the water are not harmful to the fish or plants. It isn't pH that needs to be kept stable. It is the TDS (total dissolved solids) and KH that should be stabilized. Fish can live in a wide range of pH and KH, but rapid changes in KH can be harmful to them. I suggest just using your tap water as it is, as far as KH is concerned, but adding Equilibrium (GH booster) to be sure you have a few degrees of GH, including magnesium.
 

Gerryd

Plant Guru Team
Lifetime Member
Sep 23, 2007
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South Florida
Hi Vaughn,

Up late and I took too long with my response........You beat me to it.

Hi Adam,

My substrate is 3/4 flourish and 1/4 coarse playground sand.

I hope you meant FLOURITE and sand. lol

My question: Using my pH controller, I've noticed over the course of a few weeks my pH climb in the tank from 7.6 out of the tap, to 7.9 at night after the CO2 shuts down. My GH and Kh was 1, and this pH issue occurred prior to me raising both to ~3. I'm concerned about this nighttime pH because I want to put cardinals and angels in the tank, and feel this pH is a little high.

When you dose with c02, one of the things that occurs is a lowering of the ph.

PH swings like this are not dangerous to fish, it is swings in hardness and/or temp that are deadlier.

Due to shifting c02 content, both natural and artifical waters flunctuate in their PH between day and night.

Tanks that use pressurized c02 will especially see this.

I keep > 100 cardinals and my PH goes from 7.1 to 6.2-6.3 during the day when c02 is on, with no ill effects. Before I had c02, it was 7.4-7.6 for years.

I know MANY others have the same thing.

Do yourself a favor and disconnect the ph controller to the c02 solenoid. Use the meter, but leave the solenoid on all the time. When the c02 is turned off by the controller, you lose c02 content in the water during that time.

It is better to turn c02 on 30-60 minutes PRIOR to lights on, and 30 munutes PRIOR to lights out. Just put it on a timer.

Also, is the addition of Bicarb and GH booster going to automatically raise my pH? My tap water is soft-GH/Kh 1 and pH 7.6, so I'm a little confused on the chemistry.

Yes it will, but you definitely want your water harder than it is now. I would keep up with the bicarb and gh booster.

In any event, stop worrying so much about ph.

The biggest thing IMO about high PH, is that ammonia is more toxic at higher PH than lower. When a tank is cycling, this is more of an issue. Large water changes will help this a lot to remove ammonia and other toxins.

Hope this helps.