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Old 08/27/2018, 08:41 PM   #1
BKBUTLER
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Join Date: Mar 2012
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Question Questions on using Kalkwasser and a Refugium

I already know that a refugium is a great way to naturally filter, and, while using a reverse lighting schedule and cheato bed, decrease NO3 and PO4 while reducing PH swings during DT (Display Tank) photo period OFF times. Another benefit is that the PH in tank increases with refugium photo period ON times due to CO2 reduction because of the Macroalgae of your choosing photosynthesizing nutrients that it comes in contact with.

Here is where the question comes.

If using Kalkwasser solution raises PH and ALK, does that mean it affects the cheato in my fuge, and its input nutrients? Does changing the chemical composition of the water prior to cheato filtration affect the overall end result of cheato filtration?
I.E.: lesser nutrient reduction due to the higher input ALK?

It would stand to reason that a higher ALK would cause a resultant increase in nutrient breakdown. Every organism operates more efficiently at a higher PH, to an extent, but i still feel like this question has never been answered... HELP...


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Old 10/20/2018, 10:43 PM   #2
SantaMonica
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Location: Santa Monica, California, USA
Posts: 2,479
Wow no answers. Well here...

The main pathway that higher alk may help algal growth is when rapid algal growth is limited by carbonates in the water. Algae first uses dissolved CO2 in the water to get carbon, and if growing fast this will become limiting quickly. So the algae switches to alk. Fast growing algae can reduce alk by up to 2 points a day, although usually less than 1 a day, so keeping the alk up will prevent this from being a limiting factor.


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Old 10/24/2018, 02:17 PM   #3
reefgeezer
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Join Date: Dec 2009
Location: Wichita KS
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Quote:
Originally Posted by BKBUTLER View Post
... a refugium... decrease NO3 and PO4 while reducing PH swings during DT (Display Tank) photo period OFF... ON times.
This occurs to a point but is often limited by the space needed to grow enough algae to be an effective nutrient sink.

As for pH, the "swing" is generally harmless and simply represents a slight difference in CO2 saturation levels present during photo/non-photo periods. IMO, it's much to do about nothing.

Quote:
Originally Posted by BKBUTLER View Post
...If using Kalkwasser solution raises PH and ALK, does that mean it affects the cheato in my fuge, and its input nutrients? Does changing the chemical composition of the water prior to cheato filtration affect the overall end result of cheato filtration? I.E.: lesser nutrient reduction due to the higher input ALK?...
Simply put... No. Alkalinity and the resulting pH level isn't a parameter that substantially affects the algae's growth in a reef tank. As long as there is available CO2, algae use it and have no need to use carbonates. CO2 limitation is not a real threat in a reef tank... as a matter of fact it is the opposite these days. Dissolved CO2 levels tend to be higher than they were a decade ago due to increased atmospheric CO2 levels.

Quote:
Originally Posted by BKBUTLER View Post
It would stand to reason that a higher ALK would cause a resultant increase in nutrient breakdown. Every organism operates more efficiently at a higher PH, to an extent, but i still feel like this question has never been answered... HELP...
I believe your assumption/statement here is false. Organisms don't necessarily operate more efficiently at higher pH. However, generally speaking , higher alkalinity has no effect of nutrient reduction by algae in a properly operating...normally CO2 saturated... reef tank.


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