Low pH, but high DkH/Alkalinity

[Henrik]

Hey guys,

My tank water is showing decreasing pH levels (7.8) while having sky-high alkalinity (dkH 15+). I recently read that using baking soda to increase your pH also raises your alkalinity. My LFS tells me not to worry about such a high reading of alkalinity, but I'd like to right the ship.

Coincidentally I've also has some issues with red slime algae - could it all have to do with a lack of dissolved oxygen in the tank? I've got one pump dedicated to surface agitation and one for flow within this 30 Gal Red Sea Max. Plus the skimmer. I leave the front of the hood open for better gas exchange and the hood fans are working fine...

How do I reduce the alkalinity while raising the pH to 8.1?

Thanks,


Henrik

 

[JonnyJ]

Were you treating for red slime with a remover?

 

[Henrik]

Yes, I used Red Slime Remover, and I suspect that that this was one reason for my pH to drop. How do I get it back to 8.1-8.2 without further increasing dkH?

 

[JonnyJ]

Yes, removers should be ran with an airstone and followed with a waterchange (20%?)

Either way, I would just slowly raise and get your levels in check with a series of water changes.

-jonny

 

[Cris007]

I always get a drop in Ph during winter due to keeping the windows closed and not letting enough fresh air. I try to keep at least 1 window slightly open to remedy this. Some run hoses from there skimmer air intake to outside to let fresh air in. Also 7.8 is still with in range.

 

[Henrik]

ok water changes always make sense. Even though mine don't help lower the alkalinity for some reason. I use Oceanic salt mix. Anything wrong with that particular brand?

 

[JonnyJ]

What are you testing with?

 

[reefoman]

What's your calcium and magnesium?
If your calcium is low your alk can jump up raising calcium to 430-450 you'll lower your alk. These two parameters are always dependent on each other.
Check also your magnesium it should be about 1300-1350.
As about pH, do you have sand in your tank? If so what kind of sand do you have?

Regards,
mark

 

[Henrik]

Testing with API combo kit. the bed of the tank is aragonite sand. So if my Calcium is low and I does Calcium, my Alkalinity may decrease? Not really monitoring Magnesium yet.

 

[Boomer]

Henrik.

Your LFS guy is an idiot.

The reason your pH is low and your Alk is high, is you are trying to raise the pH with a buffer. 99% of the time you never raise the pH with a buffer. Your issue is high CO2. You can add all the buffer you want and you can to stop it, the pH will still fall. You do, the pH will go up temporarily, the Alk will rise. The pH then falls again from the high CO2. You add more buffer, the Alk gets higher and the pH falls again. STOP adding buffer. 99 % of the time adding a buffer is to raise the Alk, NOT the pH.


With your Alk and using the slime remover you more than likely have high tank CO2, as Jonny pointed out.

You have 4 choices.

1. Heavy aeration of the tank to try and drive off the CO2 and get the pH back up.

2. Two large WC, 50 % ea.

3. Drip in Kalk. The Kalk will "eat" the CO2, the pH will rise with very little effect on the Alk.

4. Increase the Calcium to drive down the high Alk



I would STRONGLY suggest # 2 and NOT # 4 at all.

With your Alk your pH should be ~ 8.4-8.5

 

[Henrik]

I'm a little worried doing two 50% water changes. Don't want everything to go into shock. I do however have an airstone that I could hang in there for some time. How long should it take to adjust?

 

[Boomer]

If you keep the temp and Salinty the same it is not much of an issue at all, unless it is a SPS dominated tank with high PO4 and NO3-.

 

[Henrik]

Cool, I just tested calcium and it was about ~240. Dropped in the airstone, dosed some liquid calcium supplement and will check again tomorrow morning. So theoretically the alkalinity should drop, calcium should go up and pH should go up also...

Thanks guys!

 

[Boomer]

I don't know what is cool about it your tank is a mess and you are just going to make it worse. Your Calcium dropped because your Alk was/is so high. Your tank is waaaay out of balance. In order to drop the Alk more you need to get the Calcium way up past NSW levels and a pH above 8. Then there is the great potential of the Calcium and Alk kit giving you false readings. When the Calcium gets pulled out of solution it does this:

Ca++ + CO3-- ===> CaCO3 solid, which does not dissolve.

That solid floating around the tank will end up in your test kit sample, will get dissolved by the test kit reagents, giving false high readings.


You may already may be getting these false high Alk readings.

 

[reefoman]

Cool, I just tested calcium and it was about ~240. Dropped in the airstone, dosed some liquid calcium supplement and will check again tomorrow morning. So theoretically the alkalinity should drop, calcium should go up and pH should go up also...

Thanks guys!

Be careful, raise ca slowly
Get Salifert or Elos tests or even better Hanna checker. Sorry to say this but API should landed in your trash cane ASAP

GL
mark