Large daily PO4 swings

[Dan_P]

As I understand the operation of the Hannah checker (I use one), this inaccuracy would be eliminated by zeroing the meter on the pre-reagent water. That's the purpose of the 'C1' phase of the test procedure.

This would have nothing to do with eliminating the effect of particulates that contain phosphate, such as calcium phosphate or calcium carbonate with adsorbed phosphate.

The OP needs to take frequent measurements throughout the day to figure this one out. For example, the OP might get high measurements every other measurement throughout the day. Then we could say with more confidence the Checker or reagent needs looking into.

 

[Malum Argenteum]

This would have nothing to do with eliminating the effect of particulates that contain phosphate, such as calcium phosphate or calcium carbonate with adsorbed phosphate.

Is there any reason to think that there would be calcium phosphate particulates suspended in the water, and that they are 6x more prevalent in the PM than the AM?

Even if so, why would the fact that the phosphate is in particulate form be no less mysterious, or more useful in troubleshooting, than if it were dissolved?

 

[Shirak]

Alk is sitting around 8.3. Reagents are a month old. Vial is brand new as I just bought new ones a couple weeks ago as the indicator line was mostly gone on three of my vials. Has to be particulate. Only thing that explains the consistent results. Which means my corals prefer PO4 over .1

Use the same vile for each test and orient it in the same direction in the reader. I put a small mark at the top of the vial so I can orient it each time.

You should also be able to tell if the checker is working based on the color of the vial after shaking for 2 minutes and then hitting the 3 min. countdown on the tester. Under .1ppm phosphate and it should be faintly blue. If it's up around .6 it will be quite a dark blue and distinctly different from the other one. If you are seeing that then the tester is reading correctly. I think it's also unlikely there is a problem with reagents.

 

[Dan_P]

Is there any reason to think that there would be calcium phosphate particulates suspended in the water, and that they are 6x more prevalent in the PM than the AM?

Even if so, why would the fact that the phosphate is in particulate form be no less mysterious, or more useful in troubleshooting, than if it were dissolved?

Just a prompt for the OP to think about what is being done to the aquarium late in the day. Aquarists have routines, one or more that might result in stirring up the aquarium. Figuring out ways an analytical method can fail is not a skill most aquarists have.

 

[Randy Holmes-Farley Verified Community Expert]

As I understand the operation of the Hannah checker (I use one), this inaccuracy would be eliminated by zeroing the meter on the pre-reagent water. That's the purpose of the 'C1' phase of the test procedure.

If the particles contain phosphate and then dissolve in the test and give a real phosphate response, that is not zeroed out.

 

[Randy Holmes-Farley Verified Community Expert]

Is there any reason to think that there would be calcium phosphate particulates suspended in the water, and that they are 6x more prevalent in the PM than the AM?

Even if so, why would the fact that the phosphate is in particulate form be no less mysterious, or more useful in troubleshooting, than if it were dissolved?

Many folks dose it intentionally. It may also form when alk products are dosed.

 

[Ziggy17]

I wonder if something during the day is causing the rock to desorb phosphate. When I was dark curing the rock, the phosphate accidentally went through the roof in the container. Over 1 ppm for a couple weeks while I was away. So I know it’s in the rock. I just would think it would desorb at the same rate with the lights off as it would lights on. I can’t see it being the issue, but spit balling.

 

[Ziggy17]

I skipped the evening feeding and just tested and it read 0.

 

[Randy Holmes-Farley Verified Community Expert]

I wonder if something during the day is causing the rock to desorb phosphate. When I was dark curing the rock, the phosphate accidentally went through the roof in the container. Over 1 ppm for a couple weeks while I was away. So I know it’s in the rock. I just would think it would desorb at the same rate with the lights off as it would lights on. I can’t see it being the issue, but spit balling.

I cannot think of any reason for that to be true.

 

[Dan_P]

I skipped the evening feeding and just tested and it read 0.

Sounds like problem solved, right?

 

[EnterName]

Sounds like problem solved, right?

I mean we still don't know what about the feeding causes such high readings. I'm reasonably sure OP isn't actually adding 0.6ppm (324.6mg in OP's tank) PO₄ to the tank in one feeding session, so you are probably right that there has to be some other factor (e.g. particles in the water column caused by the feeding) that skew the results. A syringe filter might be a cheap way to test this theory.

However OP said the corals don't seem to like the current environment too much, so I wonder how we can solve this issue now.

 

[AlexandraDreadlocksPanda]

Yes, I’m lying. Lol

I didn’t say YOU were lying. I said I don’t believe those results are correct…

 

[Ziggy17]

I didn’t say YOU were lying. I said I don’t believe those results are correct…

That was me just being sarcastic :)

 

[Reckless]

Do you have a EcoTech Marine Vortech that goes into night mode or does the flow in your tank ramp down in the evening? Maybe the PO4 is settling in your tank with lower flow? I know nitrates can settle to the bottom of a tank with no flow maybe PO4 does the same.

 

[Ziggy17]

Do you have a EcoTech Marine Vortech that goes into night mode or does the flow in your tank ramp down in the evening? Maybe the PO4 is settling in your tank with lower flow? I know nitrates can settle to the bottom of a tank with no flow maybe PO4 does the same.

I do reduce the flow in the evening but because I have torches, it remains strong enough to blow them around.

 

[Randy Holmes-Farley Verified Community Expert]

Do you have a EcoTech Marine Vortech that goes into night mode or does the flow in your tank ramp down in the evening? Maybe the PO4 is settling in your tank with lower flow? I know nitrates can settle to the bottom of a tank with no flow maybe PO4 does the same.

That is not correct. Dissolved chemicals NEVER settle under normal gravity. There is too much random thermal motion, called Brownian motion, to allow for any settling.

 

[Randy Holmes-Farley Verified Community Expert]

I do reduce the flow in the evening but because I have torches, it remains strong enough to blow them around.

Flow is not impacting settling of nitrate or phosphate. They do not settle or float.

 

[mcarroll]

As the title suggests.

The past week or so, maybe 10 days, I’ve been testing my PO4 at 6pm and then at 7am and I’m seeing large swings. On average 0.7 in the evening and under 0.1 in the AM. I don’t have any macros and the skimmer is on 24/7. I don’t feed heavy. 3 times a day they get a tweezer pinch of frozen brine and a tweezer pinch of mysis. I’ve changed the battery in the Hannah checker and the process is identical for every test. NO3 remains steady at 18-20 during this 10 day period. Without any intervention I wouldn’t have thought this was possible, but I’ve replicated the results daily for over a week. Tank has a total volume of 143g so it’s large enough to not expect daily nutrient swings of this nature.

Any ideas what’s causing this?

Food. It has way more N and P than most folks realize.

https://reefs.com/magazine/aquarium-chemistry-phosphate-and-math-yes-you-need-to-understand-both/
The thing that's "weird" (but fine! ) is that you test more than once a day. Most folks test once and that's it. So you have no basis to conclude your resuts are weird because they are somewhat unique – you don't have much (anything?) to compare with. For what it's worth, your primary interest in PO4 is how low it gets....you want to prevent bottoming out as that wrecks photosynthesis and kills corals and sometime provokes dino blooms. ALL BAD STUFF. So ideally emphasize testing PO4 before feeding so you're keeping tabs on the lower levels.

Also, to clarify, are all your decimals in the right places? I ask because around 0.10 ppm is considered "high" for most people (though it's not really) and it's a decent target level that most corals seem very content with.

PO4 problems don't seem to show up until ppm's are ≥0.03 ppm – much lower. Which brings us to the next question...

The corals are not fine.
Torches are retracted, Goni reracting, zoas not happy, a stylo is starting to bleach out a bit.
That’s why I posted to look to stabilize before i start losing them.

I'm not convinced what we're talking about so far is the real issue (yet).

Can you post the rest of your water test results and maybe post a full tank shot than shows your lights and water flow sources?

Alk is sitting around 8.3. Reagents are a month old. Vial is brand new as I just bought new ones a couple weeks ago as the indicator line was mostly gone on three of my vials. Has to be particulate. Only thing that explains the consistent results. Which means my corals prefer PO4 over .1

Possible! But IMO it doesn't quite add up, at least not yet.

 

[Ziggy17]

I think my wife might have figured it out. She ,noticed something different in how I was testing. She asked why I wasn’t taking the tests from the sump. I realized that I had stopped doing that lately and drawing up straight from the DT. So perhaps that’s why I was getting high PO4 readings even a couple hours after a feed, food particulate. Everything else remains the same. I’m now seeing .08 in the evening pre last feeding test and either zero or close to zero in the morning. So I’ve stopped the skimmer tonight and hoping to see some detectable PO4 in the AM.

I’ll, run it this way for a few days and check back in. I think the corals are unhappy as the PO4 was likely zero for a week when I thought they were through the roof. I’ve since dose PO4 again to get it up to .1 ish again.

Water as it is today

Alk 8.1
Calcium 420
Mag 1425
Salinity 1.26
NO3 19
PO4 .08
Temp 77.4
PH 8 ish

I started checking twice a day as I was getting brown on the sand and was making sure I wasn’t sitting at zero to avoid Dinos.

 

[mcarroll]

I think the corals are unhappy as the PO4 was likely zero for a week

I knew something would pop up.

Besides the skimmer (and water changes?) are you doing anything else to clean or filter the tank?

Like you said, dose up now.

But getting to the root of why you're seeing PO4 drawn down to zero every day is almost just as important.

Sometimes it's excess filtration, but it happens.

What's your read on why it's so low persistently?