Lowering PO4 against rocks/sand buffering effect

[jrmailo]

Calcium carbonate binds phosphate to make something like calcium phosphate on the surface.

I suspect the boost you see is lanthanum phosphate suspended in the water, dissolving in the acid of the test kit and appearing as dissolved phosphate.

Thats very insightful thank you

 

[jrmailo]

That does not seem like a useful change relative to continuous dosing. Just dosing more, continuously, will do the trick.

I had tried dosing at larger quantity at 1 hour interval (the smallest increments that my doser allows me). But all this did was lowering my PO4 significantly before the rebound happen. for example:

On my last rebound my PO4 reached 0.41ppm. I dosed a few large doses of LaCl until my PO4 reached a desirable level. I took notes of how much LaCl it took for me to over come to reach this level. I then divide the amount by 24 hours and dosed according to my math. my results was:
Day 1: 0.35ppm (desired amount)
Day 2: 0.32ppm
Day 3: 0.27ppm
Day 4: 0.42ppm

On day 4 my PO4 rebound regardless of of my larger dose.

I could increase my dosage even more, but I am afraid that this would bring my day 2-3 to a very low level and would almost guarantee more death to my acros

 

[Randy Holmes-Farley Verified Community Expert]

Are you catching the lanthanum precipitate in a sock or something?

 

[jrmailo]

Are you catching the lanthanum precipitate in a sock or something?

I dose LaCl directly on the intake right before socks. That said, I am sure some precipitation escapes. Could this lead to such a drastic rebound?

 

[Curiousbranching]

I see, so this supports that its most likely the changes are most likely the culprit.

How long did it take for you to acclimate your acro to such level? Did you lose any on the way? And did 1ppm makes it difficult to keep new frags?

I honestly don’t remember exactly, because at the time my tank was only about 2 years old and I wasn’t really paying close attention to PO4 levels. Maybe the slow rise in PO4 gave the corals enough time to adapt.

I rarely added new frags, but when I did, they never seemed to have any issues. Like most people, I’d dip them, acclimate them, and either place them on the bottom of the tank or mount them on a frag rack.

The only thing I find a bit strange is this red algae that’s been growing really fast on the rock surfaces. It looks kind of like coralline algae, but when I touch it, it feels a bit slimy—not like regular coralline at all.

To give you a better idea of what things looked like back then, I’ll attach old photos.

 

[jrmailo]

I honestly don’t remember exactly, because at the time my tank was only about 2 years old and I wasn’t really paying close attention to PO4 levels. Maybe the slow rise in PO4 gave the corals enough time to adapt.

I rarely added new frags, but when I did, they never seemed to have any issues. Like most people, I’d dip them, acclimate them, and either place them on the bottom of the tank or mount them on a frag rack.

The only thing I find a bit strange is this red algae that’s been growing really fast on the rock surfaces. It looks kind of like coralline algae, but when I touch it, it feels a bit slimy—not like regular coralline at all.

To give you a better idea of what things looked like back then, I’ll attach old photos.

That is a stunning tank! Great job!

Incidentally, the greatest growth I had was during when I had purple cyano bacteria everywhere. As insightly as they were they must had kept things in check for me.

I eliminated them by driving PO4 down and having gobies eat them up.

 

[Randy Holmes-Farley Verified Community Expert]

I dose LaCl directly on the intake right before socks. That said, I am sure some precipitation escapes. Could this lead to such a drastic rebound?

I am not entirely sure what you are calling a rebound, but let’s say phosphate is 1 ppm and the rock surfaces are in equilibrium with it.

If you instantly drop phosphate to 0.7 ppm (or 0.9 or 0.95), then over time, starting instantly but then continuing slower and slower, phosphate comes off the rock into the water, raising the level nearly but not quite to 1 ppm. That might take place over a couple of days as phosphate in rock pores and sand works its way to the surface.

Do that again and again and the phosphate will steadily lower.

 

[jrmailo]

I am not entirely sure what you are calling a rebound, but let’s say phosphate is 1 ppm and the rock surfaces are in equilibrium with it.

If you instantly drop phosphate to 0.7 ppm (or 0.9 or 0.95), then over time, starting instantly but then continuing slower and slower, phosphate comes off the rock into the water, raising the level nearly but not quite to 1 ppm. That might take place over a couple of days as phosphate in rock pores and sand works its way to the surface.

Do that again and again and the phosphate will steadily lower.

That’s true. I can see what you are describing. This is how I would remove PO4 from rocks in a brute container. I dose and wait for PO4 to raise back up before dosing more.

But what about in a dynamic system where there’s feeding and there’s constant input of nutrients? What if the rocks and sand are constantly absorbing back PO4 before LaCl can get to them?

It would be logical to just dose more and I had been doing that for the last 3 months. But by the trend that I am seeing, it makes me think that the rocks and sand are actively sucking up PO4 from the water column. LaCl takes out even more from the water column. Almost like a double pronged attack.

 

[Randy Holmes-Farley Verified Community Expert]

That’s true. I can see what you are describing. This is how I would remove PO4 from rocks in a brute container. I dose and wait for PO4 to raise back up before dosing more. Overtime

But what about in a dynamic system where there’s feeding/

Certainly there will be ongoing additions from foods and consumption by organisms laid on top of this effect. :)

 

[jrmailo]

Certainly there will be ongoing additions from foods and consumption by organisms laid on top of this effect. :)

Sorry, my cat pushed the send button before I finished typing. Please see the bottom part of the message

 

[Curiousbranching]

I am not entirely sure what you are calling a rebound, but let’s say phosphate is 1 ppm and the rock surfaces are in equilibrium with it.

If you instantly drop phosphate to 0.7 ppm (or 0.9 or 0.95), then over time, starting instantly but then continuing slower and slower, phosphate comes off the rock into the water, raising the level nearly but not quite to 1 ppm. That might take place over a couple of days as phosphate in rock pores and sand works its way to the surface.

Do that again and again and the phosphate will steadily lower.

I’ve always wondered why PO4 reduction using LaCl happens so slowly.

In setups without a filter sock, is it possible for the skimmer to remove lanthanum phosphate precipitates? And if this precipitate settles in the tank, could it potentially release phosphate back into the water through microbial activity or some kind of chemical reaction?

Would love to hear your insights and be enlightened on this!

 

[UMALUM]

That’s true. I can see what you are describing. This is how I would remove PO4 from rocks in a brute container. I dose and wait for PO4 to raise back up before dosing more. Overtime

But what about in a dynamic system where there’s feeding/

Just spit balling here but have you been keeping an eye on your alk? Dosing this much Lanthanum without daily compensation could be a nightmare in short time on acros.

 

[jrmailo]

What if the aragonite

Just spit balling here but have you been keeping an eye on your alk? Dosing this much Lanthanum without daily compensation could be a nightmare in short time on acros.

i check alk every day and make adjustments via my calcium reactor. No issue here thank fully

 

[Randy Holmes-Farley Verified Community Expert]

Lanthanum phosphate won’t skim out unless it gets coated with organics. Thst won’t happen instantly, so it may settle out before that happens.

I’m not sure if pH gets low enough anywhere to redissolve it, but I’m not entirely sure how low the pH needs to get.

Folks use socks in an effort to protect fish like tangs, but that may or may not be useful in that context.