phosphate RAPIDLY depleting. Lanthanum excess?

[Velcro]

I don't use GFO. I do have a large refugium, but only run the light 2 hours at night. During the day yesterday I did a lot of dosing and testing of phosphate using potassium phosphate and a hanna ULR phosphorous tester. I added about 0.2ppm phosphate over the course of the day. After each addition, i would test about 10 min later and the level would be pretty close to what that addition should have caused.

here's the weird part... in a couple hours, it would drop from .08 to .02. Last night before I went to bed I adjusted it up to 0.13ppm and this morning it is undetectable (0 ppb phosphorous).

A couple months ago, I had added some lanthanum. Tank was empty so I just "eyeballed" it. I'm wondering if it's possible that I had added too much lanthanum and there is an excess in the tank which is eating the phosphate as I add it. It's the only thing in my mind that could explain the rapid depletion.

 

[Reeferdood]

FWIW,
never eyeball additives when dosing...
Sometimes you can get a false positive when dosing LC. Chances are it was lower than you thought before you made your last tweak.
I would leave it be and allow your phosphate to come back up slightly or you will likely starve your corals..
What are you trying to accomplish with having no phosphate, ULNS?
On another note, don't be alarmed if you start loosing some livestock due to the rapid decrease...
Good luck.

 

[Velcro]

FWIW,
never eyeball additives when dosing...
Sometimes you can get a false positive when dosing LC. Chances are it was lower than you thought before you made your last tweak.
I would leave it be and allow your phosphate to come back up slightly or you will likely starve your corals..
What are you trying to accomplish with having no phosphate, ULNS?
On another note, don't be alarmed if you start loosing some livestock due to the rapid decrease...
Good luck.

I'm not trying to hit zero phosphate. I just added the lanthanum while the tank was first set up because phosphate was reading like 0.3ppm and I like to be at about 0.05-0.1

 

[Reeferdood]

I see,
give it a couple days and test it again and see where you are.

 

[Randy Holmes-Farley Verified Community Expert]

It is likely binding to calcium carbonate surfaces. Rock and sand can bind massive amounts of phosphate.

One member showed the following:

https://www.reef2reef.com/threads/phosphate-absorption-rates-in-aragonite.352405/page-4#post-4501106

57 ppm of phosphate will bind to 1 pound of Florida rock from 5 gallons of water and only result in residual 0.16 ppm in the water.

 

[Velcro]

It is likely binding to calcium carbonate surfaces. Rock and sand can bind massive amounts of phosphate.

One member showed the following:

https://www.reef2reef.com/threads/phosphate-absorption-rates-in-aragonite.352405/page-4#post-4501106

57 ppm of phosphate will bind to 1 pound of Floruida rock from 5 gallons of water and only result in residual 0.16 ppm in the water.

Interesting. I was wondering about that... The tank does have 80 pounds of tropic eden dry sand

 

[tastyfish]

It is likely binding to calcium carbonate surfaces. Rock and sand can bind massive amounts of phosphate.

One member showed the following:

https://www.reef2reef.com/threads/phosphate-absorption-rates-in-aragonite.352405/page-4#post-4501106

57 ppm of phosphate will bind to 1 pound of Floruida rock from 5 gallons of water and only result in residual 0.16 ppm in the water.

This explains a lot! Thanks Randy.