Desorbing phosphate from sand with lanthanum.

[Randy Holmes-Farley]

Is there a chemical interaction between lanthanum and bleach? I’ve noticed several “stalling” events throughout this test that I’m putting it down to bacterial growth. I could use some new sand I suppose, but that’s not my preferred option.

I don’t think so, at least not a strong one, but the high pH of bleach can impact the types of orthophosphate present, and can break organic phosphates apart into inorganic phosphate.

 

[Garf]

I don’t think so, at least not a strong one, but the high pH of bleach can impact the types of orthophosphate present, and can break organic phosphates apart into inorganic phosphate.

Thanks, just wanted to make sure no obvious poisonous gas was gonna be produced or something. I wanted to treat the current sand to see if the effectiveness changes. I’ve got 2 bags of sand cycling through the regeneration process, one goes brown (even in the dark) and one that doesn’t, which I find odd. I’m starting to think that the one that goes brown doesn’t work quite as well as the one that doesn’t, but not really controlling food input, that may just be all in my head.

 

[Garf]

I decided to hold off on the bleach and took the aggressiveness down a notch. For the past fortnight I’ve been rinsing the sand before regeneration in hot tap water. This has had a dramatic impact on the effectiveness, and has eliminated the stalling previously reported. Tank phos, since stalled at 0.3ppm has reduced to 0.26 last week with a quick hot water rinse, down to 0.19ppm with a more substantial soak and agitation today. I guess bacteria don’t like hot tap water, after all

 

[Garf]

I'd be interested in the behavior around the ballpark of 0.1 ppm po4 levels that are commonly used.

I may now be in a position to give this a whirl

 

[Garf]

Update - spent a week changing out this sand for a regenerated one every other day in an effort to reduce the phos reading further. Lowest it got to was 0.17 (Hanna). I’ve reverted back to weekly regeneration now, 0.2 ish is good enough for me.

 

[taricha]

Update - spent a week changing out this sand for a regenerated one every other day in an effort to reduce the phos reading further. Lowest it got to was 0.17 (Hanna). I’ve reverted back to weekly regeneration now, 0.2 ish is good enough for me.

Do you think the limitation for doing this around 0.1 to 0.2 PPM is from the method, or from the aragonite material coming loaded with some low level of po4?

 

[Garf]

Do you think the limitation for doing this around 0.1 to 0.2 PPM is from the method, or from the aragonite material coming loaded with some low level of po4?

I imagine it would have been ok at lower levels if I hadn’t let it get to 1.4ppm initially. Something is probably still leaching from somewhere, bearing in mind I have zero mechanical filtration and no skimmer, just 1.5% daily water changes and this bag of sand. I checked the new sand for leaching, couldn’t detect anything. That may have been with the dodgy Salifert kit though.
My intrigue has now been directed towards my complaints about the sand having a bacterial film on it and my reduction in nitrates from 40 ppm to around 12ppm. I do dose mega saturated Kalkwasser at 60mls vinegar per gallon of Kalk, perhaps I’m exporting a load of bacteria simultaneously, dunno yet.

 

[Garf]

reduction in nitrates from 40 ppm to around 12ppm

Turned out I was using an uncalibrated API nitrate test in the hanna giving false hope,lol.

I tried shortcutting this process. For 3 weeks instead of rinsing the “regenerated” sand in RODI, I did a quick rinse in tapwater to remove residual lanthanum (20 or 30 seconds). It appears to have a negative impact in efficiency as tank phosphate levels rose significantly to 0.5ppm ish. So for the next 3 weeks I reverted to using RODI, and back down the phosphate level comes, slowly. Now if that means the sand is absorbing tapwater phosphate in this short period or if lanthanum is binding to the sand which is being consumed during this brief period, or something else, I’m not sure (coincidence perhaps). Whilst messing with a quarantine tank I discovered my tapwater has copper up to 1 ppm which as far as I can tell is about 40% of ionic copper used to prophylactically treat parasites, so may be just as well to reduce repeated exposure.

 

[Garf]

Right, onto a side topic regarding this bag of sand. On day 9 or 10, if I don't change the bag of sand for a regenerated one the normal gelbstoff (remember that, lol?) appears under my low lights at dusk. Upon renewal of the sand, it goes away, similar to adding activated carbon. I'll add a link that confirms binding of some organics;

https://www.sciencedirect.com/science/article/abs/pii/0016703770900037

After seeing the recent BRS video about allelopathy (surprised they mentioned algae to be honest, as folk don't want to hear that), I would like to see how effective my sand is compared to some activated carbon, which I stopped using a while back. Is there a compound I could use as an analogue for allelopathic compounds, do you think? Would food dye do it, as a rough comparison? Needs to be something I can test visually or readily get a test kit for, cheap. Thanking you all. The algae allelopathy link;

Marine Allelopathy

An article which demonstrates the complicated interactions between living things in the ocean and how some of these interactions are good, some bad. http://webs.uvigo.es/thalassas/Thalassas%2023(1)/T23(1)_04_%20Rodr%EDguez-Ramos%20et%20al.pdf

algaescrubber.net

 

[Dan_P]

Right, onto a side topic regarding this bag of sand. On day 9 or 10, if I don't change the bag of sand for a regenerated one the normal gelbstoff (remember that, lol?) appears under my low lights at dusk. Upon renewal of the sand, it goes away, similar to adding activated carbon. I'll add a link that confirms binding of some organics;

https://www.sciencedirect.com/science/article/abs/pii/0016703770900037

After seeing the recent BRS video about allelopathy (surprised they mentioned algae to be honest, as folk don't want to hear that), I would like to see how effective my sand is compared to some activated carbon, which I stopped using a while back. Is there a compound I could use as an analogue for allelopathic compounds, do you think? Would food dye do it, as a rough comparison? Needs to be something I can test visually or readily get a test kit for, cheap. Thanking you all. The algae allelopathy link;

Marine Allelopathy

An article which demonstrates the complicated interactions between living things in the ocean and how some of these interactions are good, some bad. http://webs.uvigo.es/thalassas/Thalassas%2023(1)/T23(1)_04_%20Rodr%EDguez-Ramos%20et%20al.pdf

algaescrubber.net

Welcome back! Long time.

I definitely remember reading that aragonite adsorbs organic compounds. I don’t remember reading anything about amounts though.

I use GAC to take care the gelbstoff in my system. I demonstrated in my system that even months old GAC is still effective at keeping the water colorless. Gelbstoff might be a happy coincidence in that it has a desire to bind to sand and old GAC. It might be just right chemical structure that loves to stain surfaces.

As for a test molecule for a sand-GAC smack down, you could try iodine (not iodide), or methylene blue, and the colors might be picked up by one of your Hanna Checkers. Humic acid might be useful. Gardeners use the stuff and its colored. Maybe even tea or coffee might have useful colorants, or as you wondered, just try food coloring.

Looking forwards to the results.

 

[Garf]

Welcome back! Long time.

I definitely remember reading that aragonite adsorbs organic compounds. I don’t remember reading anything about amounts though.

I use GAC to take care the gelbstoff in my system. I demonstrated in my system that even months old GAC is still effective at keeping the water colorless. Gelbstoff might be a happy coincidence in that it has a desire to bind to sand and old GAC. It might be just right chemical structure that loves to stain surfaces.

As for a test molecule for a sand-GAC smack down, you could try iodine (not iodide), or methylene blue, and the colors might be picked up by one of your Hanna Checkers. Humic acid might be useful. Gardeners use the stuff and its colored. Maybe even tea or coffee might have useful colorants, or as you wondered, just try food coloring.

Looking forwards to the results.

I'd be surprised if it works 1% as well as GAC to be honest, but I'm using 1800grammes of cleaned sand every week, which appears to be doing the trick. My head gasket blew last week which pressurised the coolant system, blowing my radiator up and warping the head, just trying to take my mind off the £2000 bill, lol.
I've got some Lugol's, think I'll try that, cheers

 

[Garf]

Back to phosphate reduction. The wife has chromis and anthias so increased feeding. She has a skimmer and a sock but the phosphate rose to 0.55ppm according to hanna. 2 weeks ago we employed the sand/ regeneration method. Week 0 - 0.55ppm, week 1 - 0.26ppm, week 2 - 0.11ppm. 2kg of sand, weekly regeneration, 240 litre tank, bare bottom, 1.5% daily waterchange, 4/5 feedings daily.

 

[areefer01]

A summary of this is;

Put sand in mesh bag in tank.
Take mesh bag out after 1 week and put it in a bucket with Lanthanum circulating for 24 to 72 hrs.
Quick rinse in RODI.
Put back into tank.

I am replying late. My apologies. Thank you for the summary. I am very curious how this might work in my system as it sounds a lot cleaner than GFO and safer than LC. My last ATI ICP result in January noted 1.7 mg/l and my Hanna kit flashed 200. So I know it is high.

I went back through the thread but may have overlooked it but what sand are you using? I have some CaribSea Florida crushed that is unused. I'm wondering how that may work.

Do you mind if I ask how you calculated how much to use? And by "quick" rinse in RODI do you mean let it soak, swish it around, empty the bag, rinse, refill, etc?

Thank you btw.

 

[Garf]

what sand are you using

Any calcium carbonate sand should work, probably finer the better (as long as it stays in the bag).

Do you mind if I ask how you calculated how much to use

I guessed

rinse in RODI do you mean let it soak

I stick it on a drainer in the kitchen pour maybe 1 litre over it and let it drain for a few seconds. Then mess with the bag a bit and pour another litre over it. After it drains, throw it in the sump.

 

[areefer01]

Any calcium carbonate sand should work, probably finer the better (as long as it stays in the bag).

Thanks. I'll have to see if I have any other. Quick check on BRS portal the Florida crushed coral grain size ranges from 3.0 to 5.5 mm. The Fiji pink or special grade is what it sounds like I need. Easy enough to go get and can always use it later.

Could also do a test and see if I notice anything. I'll have to think on this.

I guessed

Works for me. I'll have to see what sort of mesh bag I have to work with. You just toss the bag in the sump so water passes through?

I stick it on a drainer in the kitchen pour maybe 1 litre over it and let it drain for a few seconds. Then mess with the bag a bit and pour another litre over it. After it drains, throw it in the sump.

Ok, thanks. Could also make a couple bags. One to use, stand by. Swap, clean, and store. Hmm..

Well thanks. I will have to circle back and let you know how it works. The problem I have is that my Hanna checker doesn't read high phosphate. So until it gets under .6 ppm it will always flash 200. Plus I'd wager I'll be dealing with rebound from my rock and or substrate or both holding on to it. I do like this idea and test you have going on though.

Nice job.

 

[Garf]

Thanks. I'll have to see if I have any other. Quick check on BRS portal the Florida crushed coral grain size ranges from 3.0 to 5.5 mm. The Fiji pink or special grade is what it sounds like I need. Easy enough to go get and can always use it later.

Could also do a test and see if I notice anything. I'll have to think on this.



Works for me. I'll have to see what sort of mesh bag I have to work with. You just toss the bag in the sump so water passes through?



Ok, thanks. Could also make a couple bags. One to use, stand by. Swap, clean, and store. Hmm..

Well thanks. I will have to circle back and let you know how it works. The problem I have is that my Hanna checker doesn't read high phosphate. So until it gets under .6 ppm it will always flash 200. Plus I'd wager I'll be dealing with rebound from my rock and or substrate or both holding on to it. I do like this idea and test you have going on though.

Nice job.

Calcium carbonate sand for cichlid tanks may be cheaper, that's what I'm using, and it's probably 1mm to 2mm.

 

[Garf]

Previously I've mentioned about the belief that kalk reduces phosphate although I've come across no rock hard evidence beyond the theoretical. I certainly noticed rock formations in my little sand bed in the sump directly below the dosing line a while back, before I got rid of it.
I thought it was worth trying something again. I was dosing 1300 mls of kalk fortified with 90 mls of vinegar per gallon, into the aerated portion of my sump. I moved the dosing line to within 2 inches of my bag of sand (without regenerating it). Gently mixed with tank water this flows over the sand bag.

I think I'm growing rocks.

Tank pH seemed not to get quite as high as normal, and alkalinity consumption jumped a little to requiring 100 mls of vinegar in kalk along with 0.1 to 0.2 DKH 2 part daily. The interesting part is that phosphate has decreased from 0.33ppm to 0.23 in 3 days. Normally an overdue sand bag change would see a slow rise at this stage.
Thought it was worth noting anyway

Before changing the position of the dosing line I did a test with tank water, adding 1% of kalk (90mls of vinegar / gallon) and checking the phos on that. Went from 0.33 to 0.26, for what it's worth.

 

[Randy Holmes-Farley]

Previously I've mentioned about the belief that kalk reduces phosphate although I've come across no rock hard evidence beyond the theoretical. I certainly noticed rock formations in my little sand bed in the sump directly below the dosing line a while back, before I got rid of it.
I thought it was worth trying something again. I was dosing 1300 mls of kalk fortified with 90 mls of vinegar per gallon, into the aerated portion of my sump. I moved the dosing line to within 2 inches of my bag of sand (without regenerating it). Gently mixed with tank water this flows over the sand bag.

I think I'm growing rocks.

Tank pH seemed not to get quite as high as normal, and alkalinity consumption jumped a little to requiring 100 mls of vinegar in kalk along with 0.1 to 0.2 DKH 2 part daily. The interesting part is that phosphate has decreased from 0.33ppm to 0.23 in 3 days. Normally an overdue sand bag change would see a slow rise at this stage.
Thought it was worth noting anyway

Before changing the position of the dosing line I did a test with tank water, adding 1% of kalk (90mls of vinegar / gallon) and checking the phos on that. Went from 0.33 to 0.26, for what it's worth.

Yes, it has long been touted as a possible benefit, and Craig Bingman showed it in limewater itself, but not in tank water it was added to. A measure in tank water would be interesting to note, and you're growing rocks may certainly be a factor.

This is from one of my limewater articles:

What Else Does Limewater Do In An Aquarium? Reduce Phosphate

Many reefkeepers accept the concept that adding limewater reduces phosphate levels. This may be true, but the mechanism remains to be demonstrated. Craig Bingman has done a variety of experiments related to this hypothesis, and has published them in the old Aquarium Frontiers. While many aquarists may not care what the mechanism is, knowing it would help to understand the limits of this method, and how it might best be employed.

Habib Sekha (Salifert) has pointed out that limewater additions may lead to substantial precipitation of calcium carbonate in reef aquaria. This idea makes perfect sense. After all, it is certainly not the case that large numbers of reef aquaria will exactly balance calcification needs by replacing all evaporated water with saturated limewater. And yet, many find that calcium and alkalinity levels are stable over long time periods with just that scenario. One way that can be true is if the excess calcium and alkalinity that such additions typically dump into the aquarium are subsequently removed by precipitation of calcium carbonate (such as on heaters, pumps, sand, live rock, etc.).

It is this ongoing precipitation of calcium carbonate, then, that may reduce the phosphate levels: phosphate binds to these growing surfaces, and becomes part of the solid precipitate. The absorption of phosphate from seawater onto aragonite is pH dependent, with the binding maximized at around pH 8.4 and with less binding at lower and higher pH values. If the calcium carbonate crystal is static (not growing), then this process is reversible, and the aragonite can act as a reservoir for phosphate. This reservoir can inhibit the complete removal of excess phosphate from a reef aquarium that has experienced very high phosphate levels, and may permit algae to continue to thrive despite having cut off all external phosphate sources. In such extreme cases, removal of the substrate may even be required.

If the calcium carbonate deposits are growing, then phosphate may get buried in the growing crystal, which can act as a sink for phosphate, at least until that CaCO3 somehow dissolves. Additionally, if these crystals are in the water column (e.g., if they form at the local area where limewater hits the tank water), then they may become coated with organics and be skimmed out of the aquarium.

An alternative mechanism for phosphate reduction via limewater may simply be the precipitation of calcium phosphate, Ca3(PO4)2. The water in many reef aquaria will be supersaturated with this material, as the equilibrium saturation concentration in normal seawater is only 0.002 ppm phosphate. The supersaturation of calcium phosphate will be even higher in the high pH/high calcium fluid present where limewater enters reef aquaria. The locally high pH converts much of the HPO4-- to PO4---, and it is the concentration of PO4--- that ultimately determines supersaturation. That high supersaturation may tip the balance to precipitation of calcium phosphate, just as too much limewater all at once can tip the balance to precipitation of calcium carbonate. As with CaCO3, the precipitation of Ca3(PO4)2 in seawater may be limited more by kinetic factors than by equilibrium factors, so it is impossible to say how much might precipitate under reef tank conditions (without, of course, somehow determining it experimentally).

As with the precipitation of CaCO3 containing some phosphate, if these calcium phosphate crystals are in the water column (e.g., if they form at the local area where limewater hits the tank water), then they may become coated with organics and be skimmed out of the aquarium.

 

[taricha]

I certainly noticed rock formations in my little sand bed in the sump directly below the dosing line a while back, before I got rid of it.

That's interesting, that observations of even minor precipitation can be lined up with observable PO4 binding.

 

[Garf]

Turns out I don't think I was growing rocks. I had started dosing Lugol's which may have had unexpected benefits. I was unable to replicate the growing rocks thing, and phosphate rose to previous levels as I didn't change the bag out for a regenerated one. So to increase phosphate binding I've gone from 1.8kgs to 4 kgs (the mesh bags I'm using are bursting at the seams, lol), 200 ltr tank. Last test was at 0.24ppm (Hanna LR).

Edit - I would add that the vinegar in the kalk appears to be growing bacteria in the sand bag, as nitrate consumption has increased.