Desorbing phosphate from sand with lanthanum.

[Garf]

My phos level has been steadily increasing (currently at 0.75ish), whilst nitrate certainly hasn't increased, maybe even gone down a bit, which I find odd. This sand is only in the tank for a week at a time and I find it difficult to believe nitrate is being consumed within. I have noticed a slight bacterial film on the glass, so maybe the foods I'm currently adding are higher in sugars or something, dunno. I don't want to increase the amount of sand yet, or reduce feeding, so to potentially increase the unbinding effect in the regeneration bucket I've taken these steps;

a) added a small amount of sodium hydroxide to increase the pH and destroy organic materials, and aid unbinding. Resultant pH>12.5

b) added table salt to the regeneration fluid to increase the ion content which may compete with phosphate on the sand surface.

c) kept the amount of lanthanum in the regeneration fluid the same.

I have tested my regenerant from the previous (lanthanum only) run, and I'm clearly using enough lanthanum as the clear stuff after settling was zero phos, the sludge definitely was not zero.

10 hours after my first application of this new regeneration liquid has yielded this messy brown stuff, where normally it's clear/white mist. I'm assuming these are organics that have been hiding on the sand particles ? As a side note, the water in the tank appears so clear that I've stopped activated carbon use for now. 2kgs of oolitic sand, 3 litres of RODI, 150g table salt, 30 g sodium hydroxide, 25mls DIY lanthanum.

 

[Randy Holmes-Farley Verified Community Expert]

Thanks for the update. Those seem to be reasonable actions. Note too that some organics such as some humic acids can absorb more at higher pH, possibly explaining the brown.

I noticed yesterday that I still have some oolotic aragonite from the old days. If phosphate gets too high in my tank, I might mess around with it.

 

[Dan_P]

My phos level has been steadily increasing (currently at 0.75ish), whilst nitrate certainly hasn't increased, maybe even gone down a bit, which I find odd. This sand is only in the tank for a week at a time and I find it difficult to believe nitrate is being consumed within. I have noticed a slight bacterial film on the glass, so maybe the foods I'm currently adding are higher in sugars or something, dunno. I don't want to increase the amount of sand yet, or reduce feeding, so to potentially increase the unbinding effect in the regeneration bucket I've taken these steps;

a) added a small amount of sodium hydroxide to increase the pH and destroy organic materials, and aid unbinding. Resultant pH>12.5

b) added table salt to the regeneration fluid to increase the ion content which may compete with phosphate on the sand surface.

c) kept the amount of lanthanum in the regeneration fluid the same.

I have tested my regenerant from the previous (lanthanum only) run, and I'm clearly using enough lanthanum as the clear stuff after settling was zero phos, the sludge definitely was not zero.

10 hours after my first application of this new regeneration liquid has yielded this messy brown stuff, where normally it's clear/white mist. I'm assuming these are organics that have been hiding on the sand particles ? As a side note, the water in the tank appears so clear that I've stopped activated carbon use for now. 2kgs of oolitic sand, 3 litres of RODI, 150g table salt, 30 g sodium hydroxide, 25mls DIY lanthanum.

Is the water flow through the aragonite sand such that it is acting as a sand filter?

 

[Garf]

Is the water flow through the aragonite sand such that it is acting as a sand filter?

I imagine at least a little of that is going on, however, I'm washing the sand in hot water for a minute or two before the regeneration step and the bag is ultra fine, with a fine nylon mesh prefilter (but water can flow around it).

Here is the brown stuff after the sand has refiltered the solution;

 

[Garf]

Is the water flow through the aragonite sand such that it is acting as a sand filter?

For what it's worth, sand makes a fantastic particle filter. I may just employ this benefit, even if that's not the point of this thread.

Edit - I'm skeptical of the BRS experiments concluding that filtration materials/ socks etc need to be cleaned/removed every 3 days.

 

[Dan_P]

For what it's worth, sand makes a fantastic particle filter. I may just employ this benefit, even if that's not the point of this thread.

Edit - I'm skeptical of the BRS experiments concluding that filtration materials/ socks etc need to be cleaned/removed every 3 days.

Cleanliness is next to godliness :-)

 

[Garf]

Cleanliness is next to godliness :)

Let's assume that a lot of these micro particles (if that's what they are) are coral food. What happens if I deprived my coral of those? I've been thinking about particle filtration with sand for a long time. Problem being, am I gonna fix it till it's broke?

 

[Dan_P]

Let's assume that a lot of these micro particles (if that's what they are) are coral food. What happens if I deprived my coral of those? I've been thinking about particle filtration with sand for a long time. Problem being, am I gonna fix it till it's broke?

I think that the notion of over filtering an aquarium is nonsense.

 

[Garf]

I think that the notion of over filtering an aquarium is nonsense.

I think you are probably right.

 

[areefer01]

My phos level has been steadily increasing (currently at 0.75ish), whilst nitrate certainly hasn't increased,

Out of curiosity, what is your preferred number?

I think that the notion of over filtering an aquarium is nonsense.

Not sure how the trend started. I don't recall this being a thing in the late 90's when I entered. Then again as a scuba diver I see a lot of things in the water and in a high current reef crest a lot of very active and happy fish. I won't say fat because that would be mean to them. They are, however, healthy and grabbing food constantly.

 

[Garf]

Out of curiosity, what is your preferred number?

I'm determined to get it back to 0.2ppm ish. However, I'm yet to see any phosphate related problem, at any elevated level, admittedly.

 

[areefer01]

I'm determined to get it back to 0.2ppm ish. However, I'm yet to see any phosphate related problem, at any elevated level, admittedly.

Thanks. I'm in your range which is why I asked and have a similar experience. In fact oddly enough I am seeing some pretty good if not great growth on a couple of Acroporas that I have. I didn't give it much thought honestly then started to see my alkalinity struggle to stay within the 8 - 8.4 range that I normally keep it at with my current dosing levels.

Maybe related, maybe not. I honestly don't know but I do know I am back to not caring as I dislike using GFO.

Hope your day is well.

 

[Garf]

Small update. I found that autofeeders are extremely unreliable with regard to the amount they add to the aquarium, lol. It appears mine was adding twice the amount I initially tested which probably took my phosphate input to around 3 to 3.5 ppm weekly. I have corrected this by adding a weighed amount to the feeder and monitoring when it runs out.
The high pH regeneration solution appears to be good for at least 3 regenerations, just adding more lanthanum, rather than replacing the whole thing. I've restricted this to 3 regenerations due to the ugly sediment that builds up in the regeneration bucket.
This fine sand does, at least superficially appear to replace the desire to run activated carbon with great water clarity, and no yellowing that I can tell.
I would add that after 4 and a half years of flawless running I changed my return pump out for an identical one. During this procedure I sucked out all (nearly) sump detritus.
Phos (hanna, now at 0.5ppm). However, I have changed the location of the sand bag and been regenerating it every 3 or 4 days, to help out, maybe. I'll resume weekly changes when the numbers are nearer my target.

 

[Randy Holmes-Farley Verified Community Expert]

Small update. I found that autofeeders are extremely unreliable with regard to the amount they add to the aquarium, lol. It appears mine was adding twice the amount I initially tested which probably took my phosphate input to around 3 to 3.5 ppm weekly. I have corrected this by adding a weighed amount to the feeder and monitoring when it runs out.
The high pH regeneration solution appears to be good for at least 3 regenerations, just adding more lanthanum, rather than replacing the whole thing. I've restricted this to 3 regenerations due to the ugly sediment that builds up in the regeneration bucket.
This fine sand does, at least superficially appear to replace the desire to run activated carbon with great water clarity, and no yellowing that I can tell.
I would add that after 4 and a half years of flawless running I changed my return pump out for an identical one. During this procedure I sucked out all (nearly) sump detritus.
Phos (hanna, now at 0.5ppm). However, I have changed the location of the sand bag and been regenerating it every 3 or 4 days, to help out, maybe. I'll resume weekly changes when the numbers are nearer my target.

Thanks for the update!

 

[Garf]

Phos down to 0.4. I've not done the white bucket photo challenge before. What's the slight greening? One pic is my 1.5% water change, regenerated sand bag cube . The other is the wife's filter sock, skimmer, regenerated sand bag, 1.5% waterchanges, minimal activated carbon tank;

Edit, for the record, the wife's tank PO4 is testing at 0.05ppm

 

[Randy Holmes-Farley Verified Community Expert]

Might there by phytoplankton in the water?

Or a green plastic coral that is slowly leaching? lol

 

[Garf]

Might there by phytoplankton in the water?

Or a green plastic coral that is slowly leaching? lol

I was going to buy a microscope to see if I could identify anything but when I get to press the "Buy it now" button I come out in hives, lol. I'm going circulate some water with activated carbon, see if it gets rid of it.

 

[Dan_P]

I was going to buy a microscope to see if I could identify anything but when I get to press the "Buy it now" button I come out in hives, lol. I'm going circulate some water with activated carbon, see if it gets rid of it.

I’d be interested in GAC treatment results. The coloration is extremely light. Maybe fill the bucket up further to increase the color intensity.

Good call on the microscope purchase. You would have likely seen nothing.

 

[Garf]

I’d be interested in GAC treatment results. The coloration is extremely light. Maybe fill the bucket up further to increase the color intensity.

Good call on the microscope purchase. You would have likely seen nothing.

Well, this proved to be typically inconclusive, lol. Water depth is about 10 inches, water volume is 3 litres, activated carbon is one heaped tablespoon, pics taken at zero and 20 hrs, gently circulated with a magnetic stir bar. At 20hrs the carbon was covered in a bacterial fuzz. It looked to me that a bacteria coagulation had taken effect, and settled on the rough surface of the carbon. Although obviously I can't rule out the carbon acting as intended, it looked rather more, large particulate filtration, perhaps akin to the brown stuff accumulated onto filter socks (has anyone checked to see if that stuff is just bacteria?) I must say though, the aquarium looks clear.

 

[Dan_P]

Well, this proved to be typically inconclusive, lol. Water depth is about 10 inches, water volume is 3 litres, activated carbon is one heaped tablespoon, pics taken at zero and 20 hrs, gently circulated with a magnetic stir bar. At 20hrs the carbon was covered in a bacterial fuzz. It looked to me that a bacteria coagulation had taken effect, and settled on the rough surface of the carbon. Although obviously I can't rule out the carbon acting as intended, it looked rather more, large particulate filtration, perhaps akin to the brown stuff accumulated onto filter socks (has anyone checked to see if that stuff is just bacteria?) I must say though, the aquarium looks clear.

These results turned out to be more interesting than I imagined. I think you discovered what’s coloring the water. It could be bacteria, maybe a colloid, GAC adsorbing the colorant followed by bacteria bloom on the concentrated organic carbon coating the GAC surface.

If you had nothing to do, sterile filtering the water and observing the color would be telling. The filtering would remove bacteria maybe not a colloid (which makes this a less than ideal experiment).

Thanks for this. You made my day.