calcium carbonate used to bind phosphate

[ricredneck]

hi, ive been doing some reading and have read from a few sources that calcium carbonate is very good at reducing phosphate, albeit these have been on huge tests rather than in aquaria.

i live in the uk, the price of rowaphos is very steep, i have 2000l system (yeah you do the math)

my system is setup at my workplace (chemicals plant) we have an abundance of calcium carbonte im talking hundereds of tons a year. just wondering how effective it is at binding phosphate.

ive heard that the surface area of the granules of the calcium carbonate are very small when compared to gfo making it a poor binder when you compare the two, but since i have a never-ending suppy of calcium carbonate i dont have the problem of it being cost effective.

would anyone like to add their two cents, or has anyone tried it? calcium carbonate must be crazy cheap compared to US prices im sure... why cannot i find any threads on people having a go?

 

[Allmost]

I guess it would work the same way kalk bonds to po4 and percipitates.

it works theoratically.

but if your PH drops lower than 8.3, the po4 will be leached back out. I think Dr. Randy had a nice chart showing PH dependence of this.

 

[ricredneck]

I had just heard that phosphate absorbtion drops when pH is either above or below 8.4 making it less effective, rather than it leaching back in. Cant find the link though...

 

[Randy Holmes-Farley]

You may be able to bind some phosphate to columns of calcium carbonate, but the issue is going to be limited surface area, as you suggest. Calcium carbonate is not a high surface area material, so the effect will be quite small, and probably end up being more expensive than GFO.

That said, if cost is low to you, I see no reason to not try it.

It will bind a lot more magnesium than phosphate, but you have loads of magnesium in seawater to spare.