Phosphate swings throughout the day?

[cwerner]

Hello,

I'm trying to troubleshoot some interesting Hanna ULR Phosphate Checker readings that I've been receiving the past few days. Do Phosphate levels in reef tanks have 'Cycles' or level changes throughout the day? The reason I ask is because I'm doing carbon dosing in my reef tank and I've been monitoring my phosphate levels and it seems as if they swing a bit depending on when I'm doing the test.

When I would use the TM Phosphate checker I would almost always receive a phosphate test somewhere around .02. Since I want to reduce additional nitrate as a test I added an additional .02 phosphate to the tank using Brightwell NeoPhos. After dosing and letting it mix a bit I tested again with the Hanna checker and received a reading of .04, sounded perfect to me. The next couple days I started getting inconsistent test results (I'm testing very frequently right now since I'm dialing in my carbon dose to desired levels). The hanna checker read from .01 at a low all the way to .11 at a high.

I wasn't aware of any mechanism for this but can phosphate swing that much in a single day without any dosing besides regular feedings taking place?

 

[Dan_P]

Hello,

I'm trying to troubleshoot some interesting Hanna ULR Phosphate Checker readings that I've been receiving the past few days. Do Phosphate levels in reef tanks have 'Cycles' or level changes throughout the day? The reason I ask is because I'm doing carbon dosing in my reef tank and I've been monitoring my phosphate levels and it seems as if they swing a bit depending on when I'm doing the test.

When I would use the TM Phosphate checker I would almost always receive a phosphate test somewhere around .02. Since I want to reduce additional nitrate as a test I added an additional .02 phosphate to the tank using Brightwell NeoPhos. After dosing and letting it mix a bit I tested again with the Hanna checker and received a reading of .04, sounded perfect to me. The next couple days I started getting inconsistent test results (I'm testing very frequently right now since I'm dialing in my carbon dose to desired levels). The hanna checker read from .01 at a low all the way to .11 at a high.

I wasn't aware of any mechanism for this but can phosphate swing that much in a single day without any dosing besides regular feedings taking place?

Are the reading values random or do they change depending on time of day or feeding? A small amount of the variation is test variation.

 

[Randy Holmes-Farley]

Expanding on Dan's comment, I do not know if your variation is real or test variation, but you can get a better sense for that by done a bunch of tests in a span of 10 minutes, where we would not expect substantial variation.

 

[Pod_01]

Hello,

I'm trying to troubleshoot some interesting Hanna ULR Phosphate Checker readings that I've been receiving the past few days. Do Phosphate levels in reef tanks have 'Cycles' or level changes throughout the day? The reason I ask is because I'm doing carbon dosing in my reef tank and I've been monitoring my phosphate levels and it seems as if they swing a bit depending on when I'm doing the test.

When I would use the TM Phosphate checker I would almost always receive a phosphate test somewhere around .02. Since I want to reduce additional nitrate as a test I added an additional .02 phosphate to the tank using Brightwell NeoPhos. After dosing and letting it mix a bit I tested again with the Hanna checker and received a reading of .04, sounded perfect to me. The next couple days I started getting inconsistent test results (I'm testing very frequently right now since I'm dialing in my carbon dose to desired levels). The hanna checker read from .01 at a low all the way to .11 at a high.

I wasn't aware of any mechanism for this but can phosphate swing that much in a single day without any dosing besides regular feedings taking place?

So to summarize, your tank usually runs around 0.02 PO4. You added extra PO4 and after that had a reading of 0.04 PO4.
My expectations would be that if you take the reading next day at same time you should read 0.02, the extra PO4 will bind to your rock etc….
If you take additional readings during the day and you feed you should measure additional PO4 and slowly it should go back to your regular value of 0.02…. Some gets used up by bacteria other gets bound to your substrate… You are not adding extra PO4 and your tank with your regular feeding was running at 0.02.
What you observed seems reasonable, is the high value reasonable? Maybe, maybe not, I am using Hanna and there are odd readings here and there.
You can do what Randy recommends or keep measuring and see if the pattern repeats day after day.

 

[WrasseyReefer]

If you’re carbon dosing, phosphates will be consumed and lowered, along with nitrates. Food also does contribute to phosphates, especially things like reef roids and reef chili, and even frozen and dried foods. And phosphates are absorbed by rocks and sand and corals. So yes, it is normal for phosphates to fluctuate, especially if you’re carbon dosing. I carbon dose, and I also regularly dose phosphate to keep it up for coral consumption, as it’s important for coral growth. I also use Hanna ulr. You can definitely get some variations in readings with Hanna ulr as others have said, and when I do, I just repeat the test until I get a consistent number. I also verify with a second or even third phosphate test kit, such as salifert or Red Sea. It’s good that you’re testing regularly while you’re adjusting to carbon dosing. I did the same and still do as needed. Carbon dosing can be tricky to balance with feedings to get the proper balance of phosphates and nitrates. I’d even recommend testing phosphates before you dose carbon and several hours after to see how it changes.