Lanthanum to lower phosphate in rocks outside of aquarium

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kenchilada

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If the sample is not totally clear, suspended lanthanum phosphate particles may dissolve in the test, giving a false high level of dissolved phosphate.

Ahh that is a great theory, thank you. I was taking water out of my turbulent bare bottom display and the rock tub is much less flow and particulates would be more settled.

Maybe I will test display water filtered through 1 micron to see if i can produce a different result compared to the open water.
 
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Trying to decide next steps.

Most of my rock is out in the tub quickly approaching 0ppm phosphate. Now I have maybe 30 pounds of rock left in the display as well as 250G of high-PO4 water to treat.

Maybe a few large water changes, then swap the treated rock into the tank and remove the rest of untreated to the tub? I don’t want to put all the clean rock back in and have it just soak up PO4 again.

Any better ideas?

:thinking-face:
 
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Did a crappy experiment.

Filtered display water through a 1 micron sock and tested phosphate, got 7ppm. Tested unfiltered display water, got 13ppm!

Obviously these are ballpark figures due to test resolution but there is a very obvious stronger test result on the unfiltered water.

This means:
1) @Randy Holmes-Farley was correct that the test kit was returning lanthanum-bound phosphate to the water and giving false readings.
2) A 1-micron sock (or at least the sock I used) obviously does trap some portion of the precipitate after dosing lanthanum. I still cannot know if the real PO4 level is even lower.
3) Since my sailfin tang was stressed with or without the 1 micron sock, either this particular sock still leaks enough precipitate to irritate the fish, or unreacted LaCl is the irritant, or specifically some component of the Brightwell LaCl product is the irritant, or some combination of the above
 

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Did a crappy experiment.

Filtered display water through a 1 micron sock and tested phosphate, got 7ppm. Tested unfiltered display water, got 13ppm!

Obviously these are ballpark figures due to test resolution but there is a very obvious stronger test result on the unfiltered water.

This means:
1) @Randy Holmes-Farley was correct that the test kit was returning lanthanum-bound phosphate to the water and giving false readings.
2) A 1-micron sock obviously does trap some portion of the precipitate after dosing lanthanum. I still cannot know if the real PO4 level is even lower.
3) Since my sailfin tang was stressed with or without the 1 micron sock, either this particular sock still leaks enough precipitate to irritate the fish, or unreacted LaCl is the irritant, or specifically some component of the Brightwell LaCl product is the irritant, or some combination of the above
There is at least 1 experiment I've seen that sais Lanthanum phosphate particles range from 0.5 micron to 100 micron, relative to the amount of time of the reaction. So that would suggest anyone dosing into a sock above 0.5 micron is not removing much, if any immediately. However, sand filters it out very effectively, ie sand bed.
 
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There is at least 1 experiment I've seen that sais Lanthanum phosphate particles range from 0.5 micron to 100 micron, relative to the amount of time of the reaction. So that would suggest anyone dosing into a sock above 0.5 micron is not removing much, if any immediately. However, sand filters it out very effectively, ie sand bed.
Well that makes sense to me. Seems the general consensus around here is "drip LaCl into a 5 micron sock" but I doubt that accomplishes much. Plenty of others are dosing straight into tank for years. I think they just do not have fish sensitive to it.

Also I haven't added LaCl to my display in over a week and it is still strongly affecting PO4 tests. Maybe I should run some kind of sand filter to remove it? Would sand in a media reactor work? Haven't run a fluidized sand filter since the 90's.
 
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Another thought… my tang is only irritated during active dosing of LaCl, but there is clearly still significant lanthanum phosphate in the open water (skewing the test). Makes me believe it is not the lanthanum phosphate bothering him.
 
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Today I moved the remaining few large rocks in the display and was shocked to find huge detritus piles under them! I suspect tgis may be a large phosphate sink, because it was very simple to remove the phosphate from the rock I took out of the tank, yet I could not remove it when the rock was in the display.

The tank is bare bottom and I thought it was clean. This has me considering going back to sand.

I changed 40G and these are some of the buckets I siphoned out tonight!!

IMG_8035.jpeg
 
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Still working on it.

Rock in tub <0.2ppm PO4

Tank still reads 7-10ppm PO4

Makes no sense... was very easy to remove phosphate from 80% of my rock in a tub outside, but in the display tank with a few rocks I can't knock it down even blasting tons of lanthanum at it.

Could something else be a sink for PO4 other than rock? There is no sand or even detritus in the tank/sump.
 
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AND... with all the lanthanum phosphate swirling around in the water, the test kit does not work.

@Randy Holmes-Farley Is there a practical way to filter all LaPO4 precipitate from 20mL of water so I could get a clean test? Filtering through 1 micron made a difference but as @Garf pointed out LaPO4 can be <1 micron.
 

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AND... with all the lanthanum phosphate swirling around in the water, the test kit does not work.

@Randy Holmes-Farley Is there a practical way to filter all LaPO4 precipitate from 20mL of water so I could get a clean test? Filtering through 1 micron made a difference but as @Garf pointed out LaPO4 can be <1 micron.
Oddly enough, I've got a litre of stuff from my regeneration bucket settling out at the minute. It will clear visibly but I expect testing it would be open to debate. Is a positive phosphate result ultra fine lanthanum or ist it unbound phosphate?, for example. I'm gonna be testing it periodically over the next week, just out of curiosity.
 

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AND... with all the lanthanum phosphate swirling around in the water, the test kit does not work.

@Randy Holmes-Farley Is there a practical way to filter all LaPO4 precipitate from 20mL of water so I could get a clean test? Filtering through 1 micron made a difference but as @Garf pointed out LaPO4 can be <1 micron.

Just letting the sample sit for 24hrs does the trick, may be less than that but I got a zero at 24hrs with Hanna. Edit - you must avoid the stuff at the bottom of the container however, that's definitely not a zero, lol.

IMG_20240413_125409_206.jpg
 
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Just letting the sample sit for 24hrs does the trick, may be less than that but I got a zero at 24hrs with Hanna. Edit - you must avoid the stuff at the bottom of the container however, that's definitely not a zero, lol.

IMG_20240413_125409_206.jpg

Wow thanks! I didn’t think it would just settle out like that. I feel pretty silly for not trying it. I just filled a 100mL volumetric flask and I’ll test some water off the top later and let you know what happens.
 
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Just letting the sample sit for 24hrs does the trick, may be less than that but I got a zero at 24hrs with Hanna. Edit - you must avoid the stuff at the bottom of the container however, that's definitely not a zero, lol.

IMG_20240413_125409_206.jpg

Surprisingly, settling for 22 hours did not affect my results detectably. I took the sample from the top of the flask without disturbing it.
 
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I’ve been reading a lot, but there is so much anecdotal information out there it is hard to know what is true. Much of it goes back about 15 years to Reef Central where a lot of advice seemed to have started. But I’ve been around long enough to know how much good-intentioned bad information comes out of these reef forums.
 

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Surprisingly, settling for 22 hours did not affect my results detectably. I took the sample from the top of the flask without disturbing it.
I'd add a little lanthanum to the sample, shake it up and repeat tomorrow. If it reduces, in my mind that suggests it's real "free" phosphate in the water, not bound to the lanthanum.
 
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I'd add a little lanthanum to the sample, shake it up and repeat tomorrow. If it reduces, in my mind that suggests it's real "free" phosphate in the water, not bound to the lanthanum.
That’s a good idea I will try it. Im guessing something leached phosphate back out and it really is this high again. I bet if I tried your settling idea shortly after lanthanum dosing I would have seen a reduction.

Im also wondering if the way we use LaCl is wrong. Currently we dose into a sock with high flow THRU the sock. I think this causes much unreacted La to pass into the aquarium.

Maybe it would make more sense to have high recirculation within the sock (like a powerhead in the sock) but a low-flow feed into the sock. Maybe 1G every 5 minutes, to hopefully reduce how much La escapes. Then dose enough LaCl to reduce system volume by 0.5ppm PO4 over 24 hours.

Probably won’t work like I think though.
 
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Here from the side you can see how little rock is left but still 10ppm phosphate. Also notice how clean the bottom is.

Today I will remove ALL of this rock and swap with “clean” rock where PO4 reads only 0.2ppm.

Then in theory the major phosphate sink should be gone and water changes should do the trick (but I’m doubtful, I think something else unknown is happening).


IMG_8101.jpeg
 

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