Does Lanthanum chloride cause false positives?

[Miami Reef]

I need to remove phosphates which are absorbed into my rocks. The rocks are already aquascaped so I cannot do acid cures as it will break apart the bond.

So I need to strip out the phosphates once the rocks are in the display tank.

My tank is going to be 260 gallons.

I have 3 options:
GFO, Lanthanum chloride, or Phosguard.

GFO will be crazy expensive for this project. Lanthanum seems perfect, however I read that Lanthanum will cause false positives in tanks, and that sounds like a very bad thing because won’t that permanently ruin the accuracy of my test kits?

Or I could just let my tank turn into a display refugium so all the algae can consume the phosphates….. Yikes.

 

[Pistondog]

What is a false positive?
What are po4 levels?
How are you testing?

 

[mdb_talon]

I really doubt it would especially if using a low micron filter sock. In the past i have used it frequently. When i add it my phosphates go down(usually more than expected). I have added too much before and phosphates have hit 0. Again just my experience and nothing about the chemistry involved but i dont see it giving any false positive readings.

 

[Dennis Cartier]

If by false positive, you mean can it cause a Hanna checker to register a higher reading than the unbound phosphate would normally be? The answer is yes, but only if you don't adequately collect and remove the precipitate, and the tests are undertaken before the precipitate flocs have had time to settle out.

If it is an otherwise empty tank, I would definitely use LaCl and collect the precipitate. Using GFO would be too expensive if you have a lot of bound phosphate. This application is exactly what LaCl excels at.

For the readers who want to know more about the Hanna / LaCl false reading situation.

Detecting unfiltered Lanthanum Phosphate

I am wondering about the ability to detect reacted Lanthanum Phosphate in the water column. I have a LaCl filter that removes the reacted Lanthanum by passing it through a large pleated filter, but would like to research using sequential settlement stages to remove the particulate by settlement...

www.reef2reef.com

 

[Miami Reef]

@Dennis Cartier

Thank you for responding.

I use Red Sea phosphate test kits. Will that also read bound phosphates in aquariums?

Here’s my sump layout:

The tank water will flow into left side and then it will fall into the filter socks department. I have 1 micron socks that will fit.

My question, How do you recommend dripping the LaCl3? Do I dilute it prior? Any tool you recommend?

 

[Dennis Cartier]

I do not know if the Red sea or other test kits would also be able to detect the precipitate. I suspect the Hanna uses a much different method than the manual test kits, but only testing them would know for sure. In your case, I don't see it as an issue.

Here is a calculator that can help you with the dosing. Phosphate Remover Dosing Calculator

I do suggest dripping it slowly, and definitely dilute it prior to dripping to extend the dosing time. Your bound phosphate will only unbind so fast, so adding too much LaCl, too quickly will bind to alkalinity if the phosphate level has not had time to rebound from the bound surfaces. A dosing pump that can be set to a slow dosing setting comes in handy for this.

Depending on what level of phosphate you start with, it could take a bit of time to get it down. Also, once you reach the lower levels of phosphate, LaCl starts to become less efficient and somewhat ineffective. So you would want to switch to GFO once you get down to 0.1 ~ 0.15 ppm.

 

[Pistondog]

This is good for dripping diluted lc

Denshine Disposable Enteral Nutrition Bag Feeding Bag, 1200ml Enteral Delivery Gravity/Pump Feeding Bag Set, Detachable Connector

 

[Dennis Cartier]

I think I saw where you posted those in an earlier thread. I grabbed a couple as I suspect they will be perfect for hooking to a dosing pump to dose the TM K+ and A- trace elements. When a bottle is expected to last a long time, having a means to pull from it without any evaporation risk is the objective.

 

[Randy Holmes-Farley Verified Community Expert]

I think the precipitiated lanthanum phosphate will eventually settle out, filter sock or not, eliminating concern about it staying in the water and dissolving in a phosphate test.

 

[Triggreef]

I think the precipitiated lanthanum phosphate will eventually settle out, filter sock or not, eliminating concern about it staying in the water and dissolving in a phosphate test.

Is there a known cause for it to unbind from the po4 if it was not removed?

 

[Miami Reef]

Is there a known cause for it to unbind from the po4 if it was not removed?

This is what I’ve heard from people, please take this with a grain of salt. I’m genuinely interested if this is true.


I think if the ph drops very very low, the bond will break and release the phosphates.

But at that type of low PH, your stony corals, rocks etc will dissolve. It’s very rare for a PH to drop that low, and leaching phosphates will be the least of your worries if the PH does drop…your tank will probably crash in that event.


^ is this true or not? I wrote the above paragraph myself and paraphrased what I read a post say one time.

 

[Sean Clark]

This is what I’ve heard from people, please take this with a grain of salt. I’m genuinely interested if this is true.


I think if the ph drops very very low, the bond will break and release the phosphates.

But at that type of low PH, your stony corals, rocks etc will dissolve. It’s very rare for a PH to drop that low, and leaching phosphates will be the least of your worries if the PH does drop…your tank will probably crash in that event.


^ is this true or not? I wrote the above paragraph myself and paraphrased what I read a post say one time.

I was going to suggest the same thing but was waiting for RHf to reply since it was his quote.

It is my understanding that the participate cannot become unbound unless the pH is much too low for a reef tank to survive. That being said, I do not know what that pH would be.

 

[Dennis Cartier]

You can find the pH that it unbinds in here Regeneration of Lanthanum Following Precipitation of Phosphates from Waste-Waters

I can't remember the specific pH, but seem to recall it was in the 4's.

 

[Sean Clark]

You can find the pH that it unbinds in here Regeneration of Lanthanum Following Precipitation of Phosphates from Waste-Waters

I can't remember the specific pH, but seem to recall it was in the 4's.

Not a range that I would prefer to keep my reef at. Thanks for digging.

 

[damsels are not mean]

You can find the pH that it unbinds in here Regeneration of Lanthanum Following Precipitation of Phosphates from Waste-Waters

I can't remember the specific pH, but seem to recall it was in the 4's.

I'm not a fan of chasing pH but I just might if it got that low...

 

[Randy Holmes-Farley Verified Community Expert]

I don't know under what exact conditions lanthanum phosphate would dissolve (it can be calculated when it can theoretically dissolve (this calculation has been done to show that lanthanum phosphate precipitates in the deep ocean, limiting the lanthanum concentration), but whether it does so at a concerning rate under those conditions is too hard to determine without trying it.

But in general, very low phosphate, lanthanum, or low pH can encourage dissolution.

 

[Triggreef]

This is what I’ve heard from people, please take this with a grain of salt. I’m genuinely interested if this is true.


I think if the ph drops very very low, the bond will break and release the phosphates.

But at that type of low PH, your stony corals, rocks etc will dissolve. It’s very rare for a PH to drop that low, and leaching phosphates will be the least of your worries if the PH does drop…your tank will probably crash in that event.


^ is this true or not? I wrote the above paragraph myself and paraphrased what I read a post say one time.

As long as it doesn't make it inside my ca reactor then, I guess I'd not worry much. Lol