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View Full Version : Phosphate, cyano, pH and time


brad
05/03/2008, 01:05 PM
I used to have the most cyanobacteria when the lights go off. Lately I've noticed no cyano when I got home from work, so I thought my water was better. Then I noticed I had no cyano when the lights first turn on, a lot of cyno grows, and it goes away the longer the lights are on. Today, I added kalkwasser to raise my pH from 7.9 to 8.3 when the cyno was its worst, and all the cyano almost instantly disappeared.

My hypothesis is that since cyano are photosynthetic, all things being equal, there should be more the longer the lights are on, similar to how they usually act in my system. All things are not equal, photosynthesis raises the pH later in the day, causing it to drop at night enough to liberate precipitated phosphate, eliminating the cyano. The kalkwasser rapidly precipitated phosphate, also eliminating the cyano.

If this is correct, any efforts to remove phosphate from my system should be done when the pH is low. I do dose sugar or vodka for nutrient control, but do so when my pH is highest (under the assumption oxygen is also highest, and too much sugar cuts oxygen). Would I be better off dosing sugar when the pH is low? Would it be worth remove the rock without coral to a separate tank and lowering the pH to remove the phosphate and put the rock back?

Cyanobacteria add nitrogen (they are nitrifying) and carbon (they are photosynthetic) to my system, but cannot add phosphate since phosphorous is not in our atmosphere. Is it possible as much aquarists hate cyano, they are beneficial to our systems, reducing phosphate by adding carbon and nitrogen the same way adding vodka does?

Or am I way off?

Billybeau1
05/03/2008, 01:36 PM
I'm afraid you are way off.

I gotta run for now. Will explain later if someone else doesn't chime in first. :)

bertoni
05/03/2008, 09:38 PM
While cyanobacteria are growing, they consume phosphate from the water column, which can be beneficial. If the slime was harvested out of the system regularly, it'd be functional the same as harvesting a macroalga. I'm not sure it's as practical due to the surface area limitations, but the principal is identical.

If the cyanobacteria isn't removed from the system, eventually, it begins to die and rot at about the same rate it's growing, and has no net effect on phosphate.

gobyone
05/04/2008, 10:08 AM
Brad
How long have you been dosing vodka and how much do you add per dose. Ive got my po4 down but trates are still 20ppm. Thought Id give vodka a try.
Thanks
Rick

Young Frankenstein
05/04/2008, 10:33 AM
I have cyano growing in my fuge and love it !! the pods eat that stuff like if it was box of dunkin donuts in a police station !! :D
i have to clean it here and there from the top of chaeto, so that it grows only on the sides of the fuge. :D
The fuge water gets filtered before it goes back to the system.

m2434
05/04/2008, 10:55 AM
<a href=showthread.php?s=&postid=12467958#post12467958 target=_blank>Originally posted</a> by Young Frankenstein
I have cyano growing in my fuge and love it !! the pods eat that stuff like if it was box of dunkin donuts in a police station !! :D
i have to clean it here and there from the top of chaeto, so that it grows only on the sides of the fuge. :D
The fuge water gets filtered before it goes back to the system.

If the pods are eating it, it's probably diatoms. Cyano would most likely be toxic to pods...

brad
05/04/2008, 11:42 PM
I don't dose vodka/sugar regularly. I do it when nutrients are high, and I have several days in a row I can closely monitor the system, including tunning the skimmer ever few hours.

I did not mean to suggest cyano as a direct phosphate export mechanism. I meant cyano imported carbon and nitrate, which would get exported via caulerpa or skimmate and take phosphate with it.

bertoni
05/05/2008, 01:44 PM
Some types of cyanobacteria will import nitrogen, but not all, as a fairly minor detail. :)