Low PH and algae?

[sambryce]

For some reason I thought I remembered reading about this, but now I can't find it. Is there a relationship between low PH and algae growth?

Here's my problem. I moved my tank from one house to another about 3 months ago. At that time I also set up a calcium reactor and stopped dripping kalk. Everything was good for a month or so. Now I have a good bit of hair algae growing. My PH used to be approx 8.4 back when I dripped kalk and now it's 7.7-7.9 with the calcium reactor. I'm using ARM and have heard about some calcium reactor media containing phosphates.

My water tests show zero nitrate and phosphate, but the algae may be consuming it fast enough not to show up on a test.

I've got my skimmer set pretty wet and get about 8-16oz of skimmate a day.

ALK = 12 dkh
CA = 440 ppm
PH = 7.7-7.9
Temp = 80F

My Foxface, Lawnmower Blenny, snails & hermits wont touch the stuff.

Any advice, or just wait it out? I may shut down the reactor and go back to dripping kalk for a couple of months and see if that helps.

[beaslbob]

As I understand it ph lowers in the presence of carbon dioxide. Plant life consumes carbon dioxide (during lights on). So with the lights on, the algae you now have should be increasing your ph not lowering it.

[sambryce]

beaslbob....you're right.

What I'm wondering is if having a higher or lower tank PH will inhibit or contribute to algae growth.

My lower PH now is due to the calcium reactor and not dripping kalk.

[thackray]

Higher pH inhibits algae growth since there is less CO2 available.

[tooshay]

When my PH was in the 7.8 range, I had a horrible algae and cyano outbreak. As soon as I got it back up to 8.3, they both went away.

[sambryce]

I had a feeling the low PH was contributing to my algae problems. When my PH was 8.4 I had no visible signs of algae. I'll get the kalk drip going again and see how that goes.

Has anyone else seen an increase in algae growth with a PH around 7.8 vs 8.4?

Thanks for the help!

[Shoestring Reefer]

I haven't seen it in SW, but it happened to my freshwater tank.

[Randy Holmes-Farley]

This is a very complicated question.

Higher pH does not necessarily mean less CO2, although it often does. All tanks equilibrated with normal air have the same concentration of CO2, although many reef aquaria are not so equilibrated, with many aquaria having excess CO2 (and also low pH) and some having deficient CO2 (from limewater use, for example).

Also, not all algae use CO2. Some use bicarbonate instead.

Complicating the issue for aquarists is that organisms that compete with problem algae (like coralline algae and corals) will have some preference for higher pH (where calcification is easier), or at least not low pH.

Also, since alkalinity additions are a driving force in pH control in aquaria, the two effects of pH and alkalinity on algae growth are not easily seperated as they change together in many cases.

Finally, the availability of phosphate may change with tank pH.

All that said, folks have algae problems regardless of pH, and while I think a pH of 7.7 is well worth raising, I would not assume that raising it will have a big impact on an existing algae problem.

[sambryce]

Thanks for clearing that up Randy. Maybe the limewater caused the past decrease in algae and the higher PH was simply a side effect of the limewater.

I'm going to go back to using limewater for all top off water and see if that helps the hair algae.

[thackray]

Randy,

What are some good references for learning more about problem algae?

Thanks,

Phil Thackray

[Randy Holmes-Farley]

I'm going to go back to using limewater for all top off water and see if that helps the hair algae.

That sounds like a fine plan. :)

What are some good references for learning more about problem algae?


I do not know of any especially comprehensive algae articles. The team RC folks are putting together an algae faq right now, but I do not believe that it is done.

For reducing nitrate and phosphate to fight algae, try these articles:

Phosphate Issues
http://www.advancedaquarist.com/issues/sept2002/chem.htm

Nitrate Issues
http://www.advancedaquarist.com/issues/august2003/chem.htm

[thackray]

Randy

You said:

“Higher pH does not necessarily mean less CO2, although it often does. All tanks equilibrated with normal air have the same concentration of CO2, although many reef aquaria are not so equilibrated, with many aquaria having excess CO2 (and also low pH) and some having deficient CO2 (from limewater use, for example).�

It should be possible to chart pH versus alkalinity for a CO2 (specifically) equilibrated tank. (Assuming fixed atmospheric CO2, tank temperature and tank salinity). Since alkalinity does not change with CO2 variations, this would allow one to predict where an un-equilibrated tank with known pH and alkalinity would end up if we applied vigorous aeration.

I’ve wanted to ask, do you use one of the MINEQL family of programs to help model equilibrium problems?

Phil Thackray

[Randy Holmes-Farley]

It should be possible to chart pH versus alkalinity for a CO2 (specifically) equilibrated tank. (Assuming fixed atmospheric CO2, tank temperature and tank salinity).

Yes, it is,and one can make the predictions that you refer to (that's the basis of the aeration experiments that I suggest folks use to diagnose excess CO2). Here's a graph from one of my articles:

The Relationship Between Alkalinity and pH.
http://www.advancedaquarist.com/issues/may2002/chem.htm

http://www.advancedaquarist.com/images/may2002/figure1.gif

FWIW, I've seen a variety of programs relating to CO2, CaCO3, pH, etc, but I don't rtegularly use any.

[thackray]

Randy,

Thanks for the reference - everything is there. I read so many of your articles but missed this one.

Thanks again - with out you I'd be lost.

Phil Thackray

[Randy Holmes-Farley]

:thumbsup:

You're welcome. :)