Kalkwasser lowering phosphates too?

[FrugalReeferJon]

It’s been a week now since I started dosing kalkwasser and I’ve noticed that the existing hair algae in my tank is slowly dying off and is easily removed. In addition, I noticed that coralline is slowly starting to reappear. The addition of kalk was the only change I made and when I researched it more I found that the high pH from the kalk supposedly results in inorganic phosphate to bind with calcium and fall out of solution as calcium phosphate. Is this true and should I take my GFO offline to prevent phosphates from lowering too much? Also, does the calcium bind with other things that you don’t want to precipitate? Like trace and minor elements?

 

[Rocks reef]

Kalkwasser can bind phosphates to some extent, yes.

 

[Randy Holmes-Farley Verified Community Expert]

Kalk is extremely unlikely to lower phosphate too much (I used both for many years and it never got too low), and I'm not sure any effect you are seeing is from that mechanism anyway. In any case, that mechanism is hypothesized, but never actually proven to happen and there is, in general, no big change to phosphate when mist folks begin using kalk.

Are you measuring phosphate? What is it?

Rather, higher pH can boost calcifying organisms (e.g., coralline) and that boost may be outcompeting the green algae for space and trace elements.

 

[FrugalReeferJon]

Kalk is extremely unlikely to lower phosphate too much (I used both for many years and it never got too low), and I'm not sure any effect you are seeing is from that mechanism anyway. In any case, that mechanism is hypothesized, but never actually proven to happen and there is, in general, no big change to phosphate when mist folks begin using kalk.

Are you measuring phosphate? What is it?

Rather, higher pH can boost calcifying organisms (e.g., coralline) and that boost may be outcompeting the green algae for space and trace elements.

The title of my thread is a lie because I did not measure phosphate I just assumed it after reading multiple online sources about how high pH can force phosphate to fall out of solution as calcium phosphate and that my PO4 must be lowering because of the ever increasing GHA dieoff. What you said about calcifying organisms outcompeting GHA for space and resources makes sense though and I’ll definitely take that as a nice added benefit of kalk.