Why is My pH Low?

[sailmike]

I've had my 12 gallon nano with refugium up for 6 days cycling the live rock and live sand now. My pH probe gives me a reading of 7.75. The freshly mixed seawater I use tests at 8.15. I've been dosing with Kent Marine's Pro-Buffer dKH and that would bring up the pH, but then it would go right back down. Once the lights on the refugium go off, the pH goes back down to 7.75. The alkalinity is 3.5 meg/L and calcium is about 485. I don't have a magnesium test yet, it's on the way and should be here in a day or two. I've been told that the pH shouldn't be this low at any time. So, what's pulling the pH down?

Thanks,
Mike

 

[Sugar Magnolia]

It's normal for pH to swing around during the cycle. I wouldn't really bother trying to buffer it up until the cycle is over. Also, pH is lower in the morning and higher in the evening.

 

[Anonymous]

decaying matters in your tank during cycling period pull down the pH due to the consumption of oxygen, generation of CO2.

 

[zear0]

I'm pretty new to this all myself, but I've seen the following recommended a handful of times to debug a low pH problem...

Take a cup or so full of water and put an air stone in it for a few hours. Then test the pH of the water in the cup. If the pH is higher then you probably need to figure out a way to aerate your tank a little better. One way is to add more flow that disturbs the surface of the tank water. Another way would be to remove as much of your tank cover as you can. (Assuming you are covering your tank now)

My guess is deficient oxygenation isn't the root of your problem, but it might help things out a little.

Your tank hasn't been cycling all that long... What are your other parameters? NH3, NO2, NO3? Also, do you have any livestock in it besides the sand bed and rock? Are you protein skimming?

One thing to be aware of is that changing your pH drastically in a short period of time can be very harmful... This depends on your livestock, but it might be worth letting things ride themselves out for a little while longer before you try to make changes using supplements and such. Supplements may hinder the cycling process; you may fix your pH but create other problems.

Once again, I am relatively new to marine aquariums. I am sure someone more experienced will correct me if I am off base!

 

[sailmike]

Thanks for your replies. The only other life in the tank besides the rock and sand is the grape caulerpa and some red algae I don't know the name of. I am not running a skimmer, just a refugium and there is no cover on the tank so it is getting plenty of air, but I like that water in cup with airstone idea. Hmm, I would expect the ammonia, nitrite, and nitrate to be high at this time so I don't bother checking it. From most of the replies I've gotten, it seems I should just do nothing until the cycle is over.

Thanks again,
Mike

 

[Anonymous]

In this hobby, patience is one of the keys to sucess Mike. Keep us updated!

 

[sailmike]

Will do. The nano buildoff thread is great. It has given me some ideas on how I want to set up my own tank. Anyhow, the pH seems to be going up slightly even though I haven't added anything. One question, is it necessary to aerate the freshly mixed seawater?

Thanks,
Mike

 

[Anonymous]

is it necessary to aerate the freshly mixed seawater?

It's a good idea. The faster you equalized dissolved gasses the higher the quality of the water will be.

For you PH, Don't even test PH for a couple of weeks. It has no real meaning while the tank is maturing.

 

[sailmike]

Did the water-in-cup-with-airstone test and the pH sky rocketed to 7.95, so obviously high in co2. I guess all I can do now is wait for things to balance themselves out. The caulerpa is growing fast in response. I can see a number of different living things popping out of the rock not to mention a baby snail, so I wonder if I can get some micro hermit crabs to help clean up?

Mike