Phosphate Testing Confusion

TampaMark

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Tank is 4-1/2 months old. 180 gallon system with 6 fish - 2 tangs (yellow and Kole), 2 clowns, lawnmower blenny, and a melanaurus wrasse. Fish look great. Coraline algae is growing well on the dry rock in the tank. But.....added some zoas and euphyllia in the tank and none are thriving. Color is good, but no extension on the euphyllia. Zoas are a mixed bag. Two are doing well, two are doing okay, and two just look ticked off (closed tubes). Lighting is six t5s (three blues, 2 coral plus, 1 actinic). At first I thought the corals were getting too much light, so I scaled that back to just 8 hours a day and moved all corals to sand bed. No change in coral health. Scaled flow down to low flow (less than 40% from two 2k ice cap gyres on either end of the 6 foot tank. Additional 1200 gph spread to four returns (from sump) at surface of tank). No change in coral health observed after two weeks.

After more research, the advice was phosphate needed to be increased. Red sea has been testing at 0 consistently for entirety of tank life. Other parameters staying pretty consistent:
Alk 8.5
Calc 420
Mag 1400
Nitrate 4-8 ppm
Salinity 1.0255
pH 8.2

Stopped skimming a week ago, began adding phytoplankton daily, removed filter socks, feeding benepets reef food 3x per week. A reddish purple web has started covering the sand in places (see picture) in the last 3-5 days and is getting stronger. My thought was that this was probably due to my low nutrients and consistent with my thoughts about the phosphates.

My Hanna checker arrived yesterday and tested phosphate at .05 and .07 thirty minutes apart. Confusing results based on what I expected was going on in the tank. Red sea test kit still tested phosphate at 0. Not sure which result to believe. I was planning to start dosing phosphate, but now I'm not sure if that is the best course of action. The plan was to shoot for phosphate in the .03-.05 range while keeping nitrate in the 5-10 range. Decided to wait a day and test before adding anything to the tank in the morning.

Before adding phyto, Hanna tests at .04 and Red Sea still shows 0. Getting ready to vacuum my sand bed and do a water change, but not sure how to proceed after that. The coral health and the sand bed still say low nutrients, but the Hanna test has me doubting that conclusion.

Would you add phosphate, and, if so, which test kit would you believe? I feel confident I am using the test kits correctly, but the varying results are confounding. What would your next move be? Thanks for any other insights you might have.

20210415_172847.jpg
 
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AJsReef

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When dealing with low range, I trust the Hanna checkers.

That said, if you're experiencing 0s on the low range is when I would worry. I have a 180g that would test 0s even with heavy feeding until I started intentional dosing. However, I would test every 12 hours (same times daily) for 10 days after starting dosing until I got detectable levels and an idea of "consumption"

If you're getting .04-.05 you're doing fine for Phosphate, keep on keeping on :)

The Cyano should subside in a few days/week, its just exposing an imbalance likely due to the low/no Phosphate in the past
 

DoctaReef

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+1 for Hanna checker.
Also, In my experience, the hanna checker is very accurate, but wont give you the exact same results every time. If you test a sample multiple times in a row you’ll find you will get a range of readings separated by about .03 or so... but really that’s insignificant.
At your levels, I agree, Don’t add phosphate, and don’t sweat things too much right now...4 1/2 months is not a very old tank.
 
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Reef.

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+1 for Hanna checker.
Also, In my experience, the hanna checker is very accurate, but wont give you the exact same results every time. If you test a sample multiple times in a row you’ll find you will get a range of readings separated by about .03 or so... but really that’s insignificant.
At your levels, I agree, Don’t add phosphate, and don’t sweat things too much right now...4 1/2 months is not a very old tank.

My readings are not .03 apart, I have been surprised at how consistent the test has turned out to be, I was expecting fluctuations, that hasn't been my experience, I even tested back to back and got exactly the same reading.
 
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TampaMark

TampaMark

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Great feedback, thank you! I will hold off dosing phosphate. Getting back in the hobby after many years away and I feel like a newbie all over again. Patience rules the day. But that still leaves my coral looking less than happy.
 
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TampaMark

TampaMark

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My readings are not .03 apart, I have been surprised at how consistent the test has turned out to be, I was expecting fluctuations, that hasn't been my experience, I even tested back to back and got exactly the same reading.
When I tested twice yesterday, I had disturbed the sand bed in between tests. I was worried that the difference might be due to my mixing the sand bed up a bit. Todays Hanna test was only .01 off of yesterday's undisturbed sand bed test. I'll keep an eye on the consistency of the test moving forward.
 

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When I tested twice yesterday, I had disturbed the sand bed in between tests. I was worried that the difference might be due to my mixing the sand bed up a bit. Todays Hanna test was only .01 off of yesterday's undisturbed sand bed test. I'll keep an eye on the consistency of the test moving forward.

when you consider the amount we are testing for, 0.03 parts per million, yes the slightest change in testing method will throw off your result a little.
 
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TampaMark

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A tip, I fill my test vial with rodi water when not in use and store that in a small tub of rodi water too, the vial never touches tap water.
Nice tip. I will start doing that for both my phosphate and alk testers. I have been rinsing out with tap water, but will change moving forward.
 

DoctaReef

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When I tested twice yesterday, I had disturbed the sand bed in between tests. I was worried that the difference might be due to my mixing the sand bed up a bit. Todays Hanna test was only .01 off of yesterday's undisturbed sand bed test. I'll keep an eye on the consistency of the test moving forward.
What I mean is, test your same sample, after the 3 minutes, multiple times. On my checker, it varies by about .03.... for instance yesterday it read .09, .07, .09, .10, .11...
 
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TampaMark

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Leaving my phosphates alone for now. Improving my testing protocols. And going to ride the cyano bloom out.

Still leaves my corals kind of meh, but I'll keep an eye on the next several days to see what they look like.

Thanks for the input.
 

AJsReef

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What I mean is, test your same sample, after the 3 minutes, multiple times. On my checker, it varies by about .03.... for instance yesterday it read .09, .07, .09, .10, .11...

This is likely a vial issue be it finger “grease”, scratches, or orientation, etc. I’m able to get repeatable results but am very cautious about cleaning vials, not contacting anything other than the top with bare hands and make sure I place the vial in the same orientation over time.

Storing vials filled with RODI water drastically improved my testing accuracy/precision as well.
 
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Reef.

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What I mean is, test your same sample, after the 3 minutes, multiple times. On my checker, it varies by about .03.... for instance yesterday it read .09, .07, .09, .10, .11...
This is likely a vial issue be it finger “grease”, scratches, or orientation, etc. I’m able to get repeatable results but am very cautious about cleaning vials, not contacting anything other than the top with bare hands and make sure I place the vial in the same orientation over time.

Storing vials filled with RODI water drastically improved my testing accuracy/precision as well.

I would say it's more a timing issue, the reagent is meant to only be in the sample for a set length of time, if you are testing the same sample multiple times that is surely going to affect the results, not to mention you would have to zero the tester with a different vial and a different sample of salt water to that of the sample you are testing, a lot of variables there!
 
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TampaMark

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Hanna checker came in at .06 this morning. That's four readings over three days at .05, .07, .04, and .06. Feeling better about my phosphate level now. I have started rinsing the vials in RODI water and am storing them in an RODI tupperware container. Hopefully I can keep getting consistent readings moving forward.
 

Reef.

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Hanna checker came in at .06 this morning. That's four readings over three days at .05, .07, .04, and .06. Feeling better about my phosphate level now. I have started rinsing the vials in RODI water and am storing them in an RODI tupperware container. Hopefully I can keep getting consistent readings moving forward.

that's very consistent, you must have a good testing method, remember when you add food, that one feeding can add a load of PO4, you are not testing a non moving target, PO4 is always moving so your test results will too.
 
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TampaMark

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that's very consistent, you must have a good testing method, remember when you add food, that one feeding can add a load of PO4, you are not testing a non moving target, PO4 is always moving so your test results will too.
Good point. I am testing in the morning before adding anything, hoping to avoid any spikes due to recent feedings.
 

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You should also invest in the Hanna Phosphorus ULR. It is more accurate with low phos readings. One day I got a 0.00 reading on the Hanna phosphate tester and performed another test on the ULR tester and got 19 which is 0.58. Glad I have both testers, prevented me from adding phos..
 
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