How fast will rock leach or bind PO4 to reach equilibrium

[Diznaster]

I'm looking for a general estimate of how quickly the rock will leach or bind PO4. Is it days or minutes? I'm sure it depends on a lot of variables, surface area, delta between water and rock, etc..

Reason I ask is that I am trying to lower PO4. GFO has had some progress but it is slow and expensive. Yesterday I dosed enough LaCl3 (Phosphate Rx) to drop my PO4 by 0.5ppm (per the dosing instructions). Today I tested and my PO4 had only dropped about 0.05 (close to Hanna URL repeatability limits). Could the rock have leached that fast? I made a bunch of precipitate into a 10 micron filter sock.

I have seen people claim to drop PO4 from 1.5ppm to zero in a day. Maybe PO4 binds slower than it leaches and their rock does not have a repository to leach. I'm just trying to make sense of my results and would appreciate any inputs.

 

[Lovemyreef2015]

I'm not sure how long it would take. Here is a bump. #reefsquad

 

[SeaDweller]

Following along. I dosed agent green last night. I have to get a better test kit. I’m using salifert and mine is still reading 1.0. Although I am diluting it and dripping it into a 5 micron sock. I don’t see any precipitation however. Even when I drop a few drops of pure agent green stuff into the tank.

 

[Brew12]

I'm looking for a general estimate of how quickly the rock will leach or bind PO4. Is it days or minutes? I'm sure it depends on a lot of variables, surface area, delta between water and rock, etc..

Reason I ask is that I am trying to lower PO4. GFO has had some progress but it is slow and expensive. Yesterday I dosed enough LaCl3 (Phosphate Rx) to drop my PO4 by 0.5ppm (per the dosing instructions). Today I tested and my PO4 had only dropped about 0.05 (close to Hanna URL repeatability limits). Could the rock have leached that fast? I made a bunch of precipitate into a 10 micron filter sock.

I have seen people claim to drop PO4 from 1.5ppm to zero in a day. Maybe PO4 binds slower than it leaches and their rock does not have a repository to leach. I'm just trying to make sense of my results and would appreciate any inputs.

My understanding is that the process does happen fairly quickly and that it is pH dependent. If you were to take a system with high phosphates and do a 100% water change it should only take a few days for the new equilibrium to be completely formed. Much of this will happen in the first day and the process slows at it gets closer to the new equilibrium.
As to if it is possible based on what you have seen? I would say that yes, it is possible. I cannot say for sure though. If you have a large amount of substrate/rock it is more likely the cause than if you have a minimally scaped system.
I realize it is a bit of a non answer but I hope it helps.

 

[Snoopy 67]

You don't say what your levels are.
LaCl3 works better @ high levels, GFO @ low levels.
If there is enough PO4 bound in the rocks it could take some time to remove it.

 

[Reefahholic]

I’ve had it take anywhere from 4 weeks to 3-4 months. The longest was about 6 months. It really depends on the rock. Pukani Rock was notorious for leaching if not cured properly. I’ve had Walt Smith rock leach.

If you can nuke the rock in LaCI before it goes into the aquarium then it can be handled rapidly.

The problem starts if you’ve already put the rock in the tank. Then... you’ll need to use very minimal amounts of LaCI and go slowly assuming you have coral and fish in the tank. Like mentioned above, this could take weeks or even months.

W/O the coral and fish....just blast it in a vat/ stock tank. Blast....let it leach....blast....let it leach...blast...etc. You get the idea. Running a skimmer and doing large water changes will knock it out quick.

The Commercial SeaKlear is what you’ll want. I’d start with 20ml to 50 gallons in a vat.

 

[Diznaster]

My understanding is that the process does happen fairly quickly and that it is pH dependent. If you were to take a system with high phosphates and do a 100% water change it should only take a few days for the new equilibrium to be completely formed. Much of this will happen in the first day and the process slows at it gets closer to the new equilibrium.
As to if it is possible based on what you have seen? I would say that yes, it is possible. I cannot say for sure though. If you have a large amount of substrate/rock it is more likely the cause than if you have a minimally scaped system.
I realize it is a bit of a non answer but I hope it helps.

I'd call that an answer, My rockscape is on the medium heavy side. So it is entirely possible over a day that it came back close to equilibrium.

I did another dose last night and it had a greater effect 24hrs later. Here is the general progression for anyone following along:
I kept reading zero ppm on my Red Sea Pro kit, but my gut was telling me it was wrong. I got a Hanna ULR and it was 0.13ppm. I used GFO heavy for about a month and it got down to around 0.09ppm. I started with a calculated dose that should have reduced it from 0.09 to 0.01 (about 10 drops), it did nothing. My second dose reduced it to 0.08ppm after 24hrs, it was 60 drops and should have dropped it by 0.5ppm from 0.09 to -0.41 (I know negative isn't possible but that's the math). The third dose (again 60 drops) reduced it to 0.03ppm (from 0.08ppm), still not close to a 0.5ppm reduction but it moved the needle a considerable amount. I'll check it again in a few days.

 

[Diznaster]

Following along. I dosed agent green last night. I have to get a better test kit. I’m using salifert and mine is still reading 1.0. Although I am diluting it and dripping it into a 5 micron sock. I don’t see any precipitation however. Even when I drop a few drops of pure agent green stuff into the tank.

I didn't see any precipitation with a few drops in the sump either. I think it disperses so fast you don't see it. My first go with 60 drops was in the sump fairly quick and it put on quite a smoke show. The filter sock got it out after a couple hours. Second time around I did a few drops at a time in the sock, over an hour. It was hard to see in a white sock, but 3-4 drops started to become visible with a flashlight. I'm not familiar with the Salifert, but I'm in love with the Hanna Phosphorus ULR. It is very repeatable and I hate color charts that never seem to match what I see. They have one that reads in ppm Phosphate now, so you don't have to convert it. Not a big deal when you get used to it, but it was released literally on the day my Phosphorus in ppb arrived.

 

[SeaDweller]

I didn't see any precipitation with a few drops in the sump either. I think it disperses so fast you don't see it. My first go with 60 drops was in the sump fairly quick and it put on quite a smoke show. The filter sock got it out after a couple hours. Second time around I did a few drops at a time in the sock, over an hour. It was hard to see in a white sock, but 3-4 drops started to become visible with a flashlight. I'm not familiar with the Salifert, but I'm in love with the Hanna Phosphorus ULR. It is very repeatable and I hate color charts that never seem to match what I see. They have one that reads in ppm Phosphate now, so you don't have to convert it. Not a big deal when you get used to it, but it was released literally on the day my Phosphorus in ppb arrived.

So this AM I test my po4 after a straight 25 ml dose into my over flow the night before, and my po4 was about 0.1-0.25 according to my test kit. At about 7 pm, it was 0.50 ppm, so it took my rock or whatever about 12 hours or so to leach 0.25 ppm back into the water.

 

[Diznaster]

So this AM I test my po4 after a straight 25 ml dose into my over flow the night before, and my po4 was about 0.1-0.25 according to my test kit. At about 7 pm, it was 0.50 ppm, so it took my rock or whatever about 12 hours or so to leach 0.25 ppm back into the water.

That's interesting. What was it before the 25ml dose and how long was 'overnight' before you tested at 0.1-0.25? What level should the 25ml dose have achieved (assuming just water)?

I just tested again. So 3 days after 2nd 60 drop dose and 2 days after last test. It rose from 0.03 to 0.04, but I also turned GFO back on (darn extra variables). This is around the repeatability limits I've observed with the Hanna ULR, so it is essentially staying the same now.

Considering I had to do a much larger than calculated dose to get a measurable change after 24hrs and then another larger dose again to get a measurable change after 24hrs. Combined with your results of the increase after 12hrs. I think it does indicate the leaching is quite rapid, perhaps to a degree almost as fast as the LaCl3 is being dosed. And as @Brew12 suggested also dependent on the delta between water and rock/sand.

I'd be interested to know if it binds as fast as it leaches, but I'm not going to experiment with that since I'm hoping to maintain it where it is now.

 

[Diznaster]

One other thought I had regarding my initial thoughts of "How can someone drop their levels from 1.5 to zero overnight". I can see how they could, but it is probably back up to 1.25 after 2 days (unless it binds a lot slower than it leeches). I would rather maintain a somewhat constant level and not rely on LaCl3 or do smaller weekly doses if that was going to be my regular control method. The process also really disturbed my anemone and I didn't like seeing it retracted like that. It's fine now, but not the way I want to care for it.

 

[SeaDweller]

That's interesting. What was it before the 25ml dose and how long was 'overnight' before you tested at 0.1-0.25? What level should the 25ml dose have achieved (assuming just water)?

I just tested again. So 3 days after 2nd 60 drop dose and 2 days after last test. It rose from 0.03 to 0.04, but I also turned GFO back on (darn extra variables). This is around the repeatability limits I've observed with the Hanna ULR, so it is essentially staying the same now.

Considering I had to do a much larger than calculated dose to get a measurable change after 24hrs and then another larger dose again to get a measurable change after 24hrs. Combined with your results of the increase after 12hrs. I think it does indicate the leaching is quite rapid, perhaps to a degree almost as fast as the LaCl3 is being dosed. And as @Brew12 suggested also dependent on the delta between water and rock/sand.

I'd be interested to know if it binds as fast as it leaches, but I'm not going to experiment with that since I'm hoping to maintain it where it is now.

So when I began, my po4 was approx 1.0 ( or slightly more) according to salifert. I would dose between 9-10 pm and check at like 7 am. The level dropped to 0.1 to 0.25 on the first night. I dosed 25 ml for approx 250 gallons. I would then dose according to how much I needed to remove to get me to 0.0. So this morning, checked and it was 0.25 and just about 10 mins I checked and it was 0.50. So I dosed 15 ml. The cloud dissipates almost immediately. I’ve never seen any precipitation though. So unless my kit is wrong, it appears I’m leeching 0.25?

 

[SeaDweller]

So this morning I produced 0.03-0.1 ppm po4 with dosing and a filter sock last night. Let’s see if this maintains and hopefully I don’t see 0.25 this evening.

 

[Diznaster]

So when I began, my po4 was approx 1.0 ( or slightly more) according to salifert. I would dose between 9-10 pm and check at like 7 am. The level dropped to 0.1 to 0.25 on the first night. I dosed 25 ml for approx 250 gallons. I would then dose according to how much I needed to remove to get me to 0.0. So this morning, checked and it was 0.25 and just about 10 mins I checked and it was 0.50. So I dosed 15 ml. The cloud dissipates almost immediately. I’ve never seen any precipitation though. So unless my kit is wrong, it appears I’m leeching 0.25?

The cloud is the precipitation. It's just really fine and settles or gets filtered quickly. From my understanding it won't normally "re-dissolve", but it is best to get it out of tank if possible (filter sock method).

 

[SeaDweller]

The cloud is the precipitation. It's just really fine and settles or gets filtered quickly. From my understanding it won't normally "re-dissolve", but it is best to get it out of tank if possible (filter sock method).

I'm still hovering at 0.25 ppm so I'm unsure if the kit is just always reading that? I may do one more treatment, but yes I run a 5 micron sock and that seems to help for sure. Haven't lost any fish.

 

[BigJohnny]

Po4 will release out of sand and rock extremely quickly to reach equilibrium with the water. That's why water changes dont usually lower it. I'd say max 24-48hrs before equilibrium is achieved. You have to remember, you are adding a ton of po4 to your system while your dosing this LaCl, so dont solely attribute a rise back to higher levels as leaching (although that's definitely the primary cause imo). Your po4 reading in the morning may normally be much lower than at night.

@Dr. Reef had to dose lacl for a year before his rock stopped leaching to an undesirable level in the water.

 

[BigJohnny]

I'm still hovering at 0.25 ppm so I'm unsure if the kit is just always reading that? I may do one more treatment, but yes I run a 5 micron sock and that seems to help for sure. Haven't lost any fish.

Also I would recommend hanna ulr phosphorous if your dosing LaCl. A lot more accurate so you can have a better idea of what's going on.

 

[madweazl]

@jda did some work on this a while back but I dont remember the title of the post.

 

[jda]

Uusally within about 48 hours once the easily exposed structure of the rock has been bound up a bit. The binding starts instantly, but the can take a while to reach the nooks and crannies.

Like others said, it can take a lot. A local needed two 5g buckets of GFO to get the rock in his 180 down to normal levels.

 

[Diznaster]

Po4 will release out of sand and rock extremely quickly to reach equilibrium with the water. That's why water changes dont usually lower it. I'd say max 24-48hrs before equilibrium is achieved. You have to remember, you are adding a ton of po4 to your system while your dosing this LaCl, so dont solely attribute a rise back to higher levels as leaching (although that's definitely the primary cause imo). Your po4 reading in the morning may normally be much lower than at night.

@Dr. Reef had to dose lacl for a year before his rock stopped leaching to an undesirable level in the water.

Can you please describe how adding LaCl3 adds "a ton of PO4". Lanthanum is an element metal, Chlorine is an element halogen. There is no Phosphorus is LaCl3, so how does it add any PO4?