pH issues...

[tjm80]

I have a 75 gallon reef tank with about 75-80 lbs live rock, 3-4 inch sandbed, 20 gallon long sump (reverse lighting schedule for cheato). I can't seem to get my pH above 8.0 (tested at the end of the day). My dKH is around the 8/9 range and calcium is around 420-440. All test kits are API. I'm using an in sump protein skimmer which should be oxygenating the water, and I have one powerhead and my return agitating the surface of the display tank and the pH refuses to move.

I've thought about dosing kalk in my ATO to raise it up a little, but wouldn't that make my calcium shoot too high? I'm doing weekly 10 gallon water changes, and plan to switch to reef crystals when I run out of salt. I'm using Coralife sea salt right now, because it was the only salt they had available last time I needed to buy any, and it was on clearance for half off.

I realize that 8.0 pH is on the low end of acceptable but also that pH drops when the lights are out. And my pH does drop at night to 7.8 or 7.6 according to the API kit.

Any suggestions are more than welcomed!!

 

[AquaRick]

I had a similar issue with instant ocean. Switched to reef crystals and pH has been holding steady at 8.2-8.4 even at night. Do you have an open top? Is there anyway you can get your water tested by a different brand of test kit? Maybe have your LFS test your water? Even if they use API, at least it would be a second opinion etc.

 

[carey]

My tanks ph runs at 7.7 to 8.0 by the end of the day. i would just accept the low ph and go about your business. Your test results for calcium and alkalinity dont' show a need to dose yet so I would just enjoy the tank. Messing with kalk isn't to be taken lightly as it's some powerful stuff. I lost 2 sps when i started using Kalk and I attribute it to the kalkwasser.

I've asked several times on this forum about my low ph and most people have said to just let it be.

 

[Gregcoyote]

I think it is a bit low. I would adjust your alkalinity (KH) first to help buffer and reduce the swinging. I would not recommend Kalkwasser at this time as you could really mess things up. Study this a bit more and look into buffers that can gradually stabilize the system. Be sure you have a lot of air movement on the surface for gas exchange...that is a big reason for ph drops. Also vacuum out accumulated debris as that can cause the tank to go acidic as well.

I have used Kalkwasser for many years and it is very good when done right. Slowly...
But I don't think you are there yet.

 

[tjm80]

Just got home with the reef crystals and will mix up a batch for my next PWC. The tank isn't covered and one powerhead and my return are both pointed toward the surface to agitate the water.

Also my alk. has been low (around 7ish) until I started putting some baked baking soda in my topoff water.

I took a water sample to the LFS when I got the reef crystals and all my readings came out fine except pH (8.0) and magnesium (1000)