Dosing phosphate causing leaching live rock?

[rynosreef]

Hey all, my question is this: is the concentration of bound phosphate in live rock substantially higher than the surrounding water? And could this cause STN.

My tank has been running for a couple years. It’s small so besides water changes and a skimmer I’ve not found a need for GFO, carbon dosing etc.

Recently though I found a few of my acros colors were looking faded and light. So I reduced my light intensity and increased feeding to my fish. My phosphate tested 0 on Hanna ULR checker, so in addition to the reduced light intensity and extra feeding, I started dosing NeoPhos to bring up my phosphate.

It took a lot of dosing over a long time to get consistently detectable phosphate. From what I’ve researched this is because the live rock binds most of it until a state of equilibrium is reached, then it acts as more of a buffer.

My phosphate is now a consistent 0.028. My coloration, and Alk uptake did improve so I’ve felt the changes were the right call. Although I honestly can’t say for sure if it was the lighting change or the feeding/phosphate dosing, or both that led to the improvement.

My issue started when I moved some frags from a frag rack to the live rock. On the rack the acros we’re doing great, encrusting and basing out quickly. A day after mounting to the live rock I started noticing STN from the base, quite literally from the point of the tissue closest to the rock.

My suspicion is that although the concentration of phosphate in the water is 0.028, the concentration in the rock is much higher and perhaps this is the cause of the frags STN when mounted to the rocks.

Does that sound plausible or should I keep digging?

Thanks!

 

[schuby]

What measurement unit is your Hanna phosphate checker? Ppb or ppm?

 

[rynosreef]

It’s ppb. I also have the Hanna standard to see how accurate it is. The standard is 100ppb and my checker is usually around 96ppb.

 

[chipmunkofdoom2]

My suspicion is that although the concentration of phosphate in the water is 0.028, the concentration in the rock is much higher and perhaps this is the cause of the frags STN when mounted to the rocks.

This is not how phosphate binding works. If the phosphate in your water column drops and some phosphate unbinds from the aragonite, it will quickly distribute evenly throughout the entire water column. It will not hang around one spot and burn a coral.

 

[Dan_P]

Hey all, my question is this: is the concentration of bound phosphate in live rock substantially higher than the surrounding water? And could this cause STN.

My tank has been running for a couple years. It’s small so besides water changes and a skimmer I’ve not found a need for GFO, carbon dosing etc.

Recently though I found a few of my acros colors were looking faded and light. So I reduced my light intensity and increased feeding to my fish. My phosphate tested 0 on Hanna ULR checker, so in addition to the reduced light intensity and extra feeding, I started dosing NeoPhos to bring up my phosphate.

It took a lot of dosing over a long time to get consistently detectable phosphate. From what I’ve researched this is because the live rock binds most of it until a state of equilibrium is reached, then it acts as more of a buffer.

My phosphate is now a consistent 0.028. My coloration, and Alk uptake did improve so I’ve felt the changes were the right call. Although I honestly can’t say for sure if it was the lighting change or the feeding/phosphate dosing, or both that led to the improvement.

My issue started when I moved some frags from a frag rack to the live rock. On the rack the acros we’re doing great, encrusting and basing out quickly. A day after mounting to the live rock I started noticing STN from the base, quite literally from the point of the tissue closest to the rock.

My suspicion is that although the concentration of phosphate in the water is 0.028, the concentration in the rock is much higher and perhaps this is the cause of the frags STN when mounted to the rocks.

Does that sound plausible or should I keep digging?

Thanks!

If the water was absolutely stagnant AND you carefully sampled the water at the rock surface AND used a very sensitive test for phosphate, you might see a bit more phosphate at the surface of the rock than in the bulk water. So your idea is OK but unlikely to be relevant to solving your problem.

A much simpler explanation is that the frags were borderline sick and the shock of moving them to new water just pushed them over the edge.

 

[BradB]

Not sure why anyone would dose phosphate on purpose, but stn in new frags is likely what Dan said. I've found with Acropora especially, turning around borderline frags and corals is almost impossible. It might die slower with perfect lighting and flow, but it rarely recovers, when frags from a tank I know is thriving almost always grow and do well, at least initially.

 

[rynosreef]

This is not how phosphate binding works. If the phosphate in your water column drops and some phosphate unbinds from the aragonite, it will quickly distribute evenly throughout the entire water column. It will not hang around one spot and burn a coral.

Thanks! I guess my thinking is that the phosphate that was dosed to the tank went somewhere. It certainly wasn’t all taken up by the corals, I don’t have algae, and it’s not in the water column, at least not at the total amount that was dosed over weeks to get consistently detectable levels. Leading my thinking to be that it’s bound to some degree in the rock.

Haha for an admittedly terrible visual: like a glowing green radioactive rock, constantly at a higher concentration of phosphate than the surrounding water.

 

[rynosreef]

If the water was absolutely stagnant AND you carefully sampled the water at the rock surface AND used a very sensitive test for phosphate, you might see a bit more phosphate at the surface of the rock than in the bulk water. So your idea is OK but unlikely to be relevant to solving your problem.

A much simpler explanation is that the frags were borderline sick and the shock of moving them to new water just pushed them over the edge.

Thanks Dan! The thing is I had the frags on the rack for several weeks. I always place new frags on the rack and wait until I see growth, basing out etc. These frags had been in my system for about a month on the rack and we’re basing out and starting to grow into the rack. That’s why I felt they were ready for mounting to the rock. I agree it could be something other than phosphate. But I’m not sure these frags were borderline sick.

 

[rynosreef]

Not sure why anyone would dose phosphate on purpose, but stn in new frags is likely what Dan said. I've found with Acropora especially, turning around borderline frags and corals is almost impossible. It might die slower with perfect lighting and flow, but it rarely recovers, when frags from a tank I know is thriving almost always grow and do well, at least initially.

Thanks Brad! I guess my confusion is that these frags were from a healthy system and were starting to encrust into my frag rack, which they had been on for about a month for monitoring. So I don’t feel they were borderline sick, quite the opposite actually. It seems something about the move ticked them off more so than usual. And the dosing is the only variable that seems odd.

At any rate I’m not dosing now, and have them back on the rack. I’m going to leave them alone and see how they do.

 

[Saltyreef]

Could be directly related to par. Edges of tank have substantially less par than the center where the rock work generally is.
A lot of hobbiests unknowingly run their lights too bright.
Ask me how i know

 

[rynosreef]

Could be directly related to par. Edges of tank have substantially less par than the center where the rock work generally is.
A lot of hobbiests unknowingly run their lights too bright.
Ask me how i know

Haha for sure! When I first noticed the faded colors I reduced my light intensity, thinking that was it. And sure enough my Alk uptake went up so I definitely think the lights were up too high initially. Since then though the color came back so I’m not sure if that’s sit, but it certainly could be.

I think for me the red herring was this:

I mounted one of the frags still on its frag plug, which it had fully encrusted. I mounted it at an angle since it’s a tabling acro. The side that touched the rock look ticked the next day and has been the side showing tissue loss. The side facing the light is doing fine. Could be coincidence but it got me thinking.

 

[Randy Holmes-Farley]

Not sure why anyone would dose phosphate on purpose,

Because some folks have excessively low phosphate and run a risk of dinos.

 

[rynosreef]

Because some of folks have excessively low phosphate and run a risk of dinos.

I forgot to mention it but this was in part why I started dosing phosphates. Colors were faded and I was seeing some dinos here and there. It was never an outbreak or anything but since dosing they’ve gone away.

 

[Semisonyx]

Two things:

One, higher par in the center of the tank compared to the position of your frag rack like @Saltyreef said could be the issue.

Second, dosing phosphate can cause nitrates to plummet to 0, especially if you had been showing 0 ppb on Hanna before dosing. Test your nitrates and consider dosing accordingly. However, if you dose NO3, keep an eye PO4 until they balance out. Test both daily until they stabilize.

IME, zero PO4 or NO3 has been the cause of STN/RTN 99% of the time when a sudden alkalinity fluctuation wasn’t the cause.

 

[Dan_P]

Thanks Dan! The thing is I had the frags on the rack for several weeks. I always place new frags on the rack and wait until I see growth, basing out etc. These frags had been in my system for about a month on the rack and we’re basing out and starting to grow into the rack. That’s why I felt they were ready for mounting to the rock. I agree it could be something other than phosphate. But I’m not sure these frags were borderline sick.

OK, my hypothesis seems to be on the ropes

How about light intensity challenges?

 

[rynosreef]

OK, my hypothesis seems to be on the ropes

How about light intensity challenges?

It's a possibility for sure. I tried my best to match the relative PAR levels when placing them. And it seems to be effecting some corals that have been in the tank for a while.

If the water was absolutely stagnant AND you carefully sampled the water at the rock surface AND used a very sensitive test for phosphate, you might see a bit more phosphate at the surface of the rock than in the bulk water. So your idea is OK but unlikely to be relevant to solving your problem.

Dan, I think you might be onto something. I sampled the water close to the rock with the Hanna ULR checker and got 25ppb (0.077ppm), this was with the pumps on actually as I forgot to turn them off. I then checked the bulk water and it read 0.00ppm. It not perfect by any means I know, but maybe it's something? I'm not sure if normally that would be a meaningless discrepancy, but it seems meaningful considering we've been out of town for a few days and the fish weren't fed, no phosphate was dosed etc. And recently when I've gotten a 0.00ppm reading I'd go and dose phosphate.

Earlier this morning I moved several acros back onto the frag rack and tonight I noticed that the tissue loss on them has stopped. However, some of the acros still on the rock have continued to show tissue loss, including some that are well established corals/not recently added. So I've moved any that can be moved onto the rack in hopes they'll improve. We'll see in the AM.

It may not be the rock/phosphate thing. It just seems strange that some of these were encrusting into the frag rack one day and then receding a day after being mounted to the rock. And the only outlier I see is that I've been dosing phosphate for weeks to try to help coloration/keep detectable levels. Maybe I turned my rock into this:

D'oh! hehehe

 

[Dan_P]

It's a possibility for sure. I tried my best to match the relative PAR levels when placing them. And it seems to be effecting some corals that have been in the tank for a while.



Dan, I think you might be onto something. I sampled the water close to the rock with the Hanna ULR checker and got 25ppb (0.077ppm), this was with the pumps on actually as I forgot to turn them off. I then checked the bulk water and it read 0.00ppm. It not perfect by any means I know, but maybe it's something? I'm not sure if normally that would be a meaningless discrepancy, but it seems meaningful considering we've been out of town for a few days and the fish weren't fed, no phosphate was dosed etc. And recently when I've gotten a 0.00ppm reading I'd go and dose phosphate.

Earlier this morning I moved several acros back onto the frag rack and tonight I noticed that the tissue loss on them has stopped. However, some of the acros still on the rock have continued to show tissue loss, including some that are well established corals/not recently added. So I've moved any that can be moved onto the rack in hopes they'll improve. We'll see in the AM.

It may not be the rock/phosphate thing. It just seems strange that some of these were encrusting into the frag rack one day and then receding a day after being mounted to the rock. And the only outlier I see is that I've been dosing phosphate for weeks to try to help coloration/keep detectable levels. Maybe I turned my rock into this:

D'oh! hehehe

LOL

Nice detective work. Moving some of the frags back to the rack was a productive idea. If you figure this one out, hope you post the solution.

 

[Randy Holmes-Farley]

It's a possibility for sure. I tried my best to match the relative PAR levels when placing them. And it seems to be effecting some corals that have been in the tank for a while.



Dan, I think you might be onto something. I sampled the water close to the rock with the Hanna ULR checker and got 25ppb (0.077ppm), this was with the pumps on actually as I forgot to turn them off. I then checked the bulk water and it read 0.00ppm. It not perfect by any means I know, but maybe it's something? I'm not sure if normally that would be a meaningless discrepancy, but it seems meaningful considering we've been out of town for a few days and the fish weren't fed, no phosphate was dosed etc. And recently when I've gotten a 0.00ppm reading I'd go and dose phosphate.

Earlier this morning I moved several acros back onto the frag rack and tonight I noticed that the tissue loss on them has stopped. However, some of the acros still on the rock have continued to show tissue loss, including some that are well established corals/not recently added. So I've moved any that can be moved onto the rack in hopes they'll improve. We'll see in the AM.

It may not be the rock/phosphate thing. It just seems strange that some of these were encrusting into the frag rack one day and then receding a day after being mounted to the rock. And the only outlier I see is that I've been dosing phosphate for weeks to try to help coloration/keep detectable levels. Maybe I turned my rock into this:

D'oh! hehehe

One possible complication to that "near rock" collection may be particulate matter boosting the apparent absorbance by light scattering, and hence giving a false high phosphate signal.

 

[Dan_P]

One possible complication to that "near rock" collection may be particulate matter boosting the apparent absorbance by light scattering, and hence giving a false high phosphate signal.

The other possibly, which I thought you were going to describe, is that the particulates themselves are PO4 rich. Under acidic conditions of the PO4 test, these particulates would dissolve or leach PO4, enough to elevate the reading.

 

[rynosreef]

One possible complication to that "near rock" collection may be particulate matter boosting the apparent absorbance by light scattering, and hence giving a false high phosphate signal.

The other possibly, which I thought you were going to describe, is that the particulates themselves are PO4 rich. Under acidic conditions of the PO4 test, these particulates would dissolve or leach PO4, enough to elevate the reading.

I think you both are correct. I’ve continued to test periodically over the past couple days and haven’t been able to repeat the higher PO4 result “near” the rock.

My recent tests of the water column have come back 0.03, 0.02, and 0.04. The ULR was checked against a 100ppb standard and came back at 98ppb. So I generally trust those results and they indicate acceptable phosphate. And they’re consistent from day to day. So I don’t think anymore phosphate needs to be dosed at least.

I looked over my notes from the past few weeks. Since I increased feeding, dosed phosphates, and reduced the light intensity, my acro colors absolutely improved, my live rock is darker, coralline is growing faster, the small amount of dinos are gone, I even have some a small amount of welcome GHA here and there. So ultimately I think the changes were successful in that regard.

Still the tissue lose happened for a reason though. Possibly simply from the positive changes.
However I did come across something interesting in my notes. I test Alk daily and usage has been consistent. However I used some Aiptasia X about a week and a half ago, a lot of it, to wipe out some aiptasia. The following 3 days Alk consumption stopped. Maybe this episode of tissue loss is a delayed reaction to that.

At any rate what could be moved to the rack is there now. It’s definitely sloooooow tissue necrosis fortunately, so if I can keep things stable hopefully they’ll recover with time.