High variance in PO4 readings

[Forty-Two]

Hi - I’m looking for some ideas on what might going on with my PO4 numbers. I do have a theory but I’d like to see what comes out of the discussion.


At night it appears my PO4 varies between .101 and .03. During the day I’m seeing numbers between .08 and .15

When my PO4 is spiking I can see the difference in the corals which is leading me to do additional testing (Polyp retraction, change in colouration)

Testing wise - I use the Master Tronic with the Tropic Marin Pro PO4 testing kit, and the Hanna PO4 ULR tester. Originally I had some inconsistencies in the readings until I fixed the PO4 Master Tronic vial (sulphuric acid had eaten through the lid and polluted the reagent) - and now they are fairly consistent with each other so I’ve ruled out the test kits being the issue.


I do carbon dose Elimini NP which does over time lower PO4 nicely however I stopped carbon dosing for a couple of months during my dinoflagellates battle. Similarly I also stopped
my skimmer during this period. Regardless for the last 8 months or so (which is a time period outside of the dinoflagellates battle) the PO4 has been consistently up and down in an unpredictable manner.

I do use live rock from 2 different sources - both sources got them from the ocean a few years ago and since then they havein tanks (Indonesian).

I have live rock both in the sump and in the tank - probably more lbs/gallon than I need. The sand bed is very much alive and healthy. I have a goby that cleans it nicely.

The only thing I can see as being a possible cause is I use an alternating light schedule for the refugium. The refugium has no Chaeto in it - but live rocks, snails and copepods. There is a small amount of algae as well but nothing major.

I feed once a day - 3 cubes for a tang, wrasse, 2xclowns and a goby. It’s a little heavy but my bio load is pretty light
I really don’t know what’s causing such a big variance but it is impacting the health of the corals.


Thanks In advance for your suggestions and insights

 

[gbroadbridge]

Hi - I’m looking for some ideas on what might going on with my PO4 numbers. I do have a theory but I’d like to see what comes out of the discussion.


At night it appears my PO4 varies between .101 and .03. During the day I’m seeing numbers between .08 and .15

When my PO4 is spiking I can see the difference in the corals which is leading me to do additional testing (Polyp retraction, change in colouration)

Testing wise - I use the Master Tronic with the Tropic Marin Pro PO4 testing kit, and the Hanna PO4 ULR tester. Originally I had some inconsistencies in the readings until I fixed the PO4 Master Tronic vial (sulphuric acid had eaten through the lid and polluted the reagent) - and now they are fairly consistent with each other so I’ve ruled out the test kits being the issue.


I do carbon dose Elimini NP which does over time lower PO4 nicely however I stopped carbon dosing for a couple of months during my dinoflagellates battle. Similarly I also stopped
my skimmer during this period. Regardless for the last 8 months or so (which is a time period outside of the dinoflagellates battle) the PO4 has been consistently up and down in an unpredictable manner.

I do use live rock from 2 different sources - both sources got them from the ocean a few years ago and since then they havein tanks (Indonesian).

I have live rock both in the sump and in the tank - probably more lbs/gallon than I need. The sand bed is very much alive and healthy. I have a goby that cleans it nicely.

The only thing I can see as being a possible cause is I use an alternating light schedule for the refugium. The refugium has no Chaeto in it - but live rocks, snails and copepods. There is a small amount of algae as well but nothing major.

I feed once a day - 3 cubes for a tang, wrasse, 2xclowns and a goby. It’s a little heavy but my bio load is pretty light
I really don’t know what’s causing such a big variance but it is impacting the health of the corals.


Thanks In advance for your suggestions and insights

Well PO4 would be highest after feeding, before the other organisms get a chance to consume it.

I always test at 7am - before feeding and after everything has been working overnight.

 

[Forty-Two]

Well PO4 would be highest after feeding, before the other organisms get a chance to consume it.

I always test at 7am - before feeding and after everything has been working overnight.

Mine isn’t highest after feeding - that’s when it starts to come down. It continues its downward trend during the day until night where it seems to almost bottom out and then spikes at around 4 am. After that it remains high until feeding time and then seems to come down after.

 

[Reef and Dive]

Mine isn’t highest after feeding - that’s when it starts to come down. It continues its downward trend during the day until night where it seems to almost bottom out and then spikes at around 4 am. After that it remains high until feeding time and then seems to come down after.

Yeah it takes hours to rise after feeding. Our PO4 does vary more than we think. I measured over hours many days in the past, and stopped feeding corals too often, once a week seems pretty good to me now…

 

[gbroadbridge]

Mine isn’t highest after feeding - that’s when it starts to come down. It continues its downward trend during the day until night where it seems to almost bottom out and then spikes at around 4 am. After that it remains high until feeding time and then seems to come down after.

That's interesting.

I was surprised when I installed automatic Alk measurement how much that bounced around over 24 hours, so I suppose the same must be true of other parameters.

I ended up cutting back the testing schedule because I started going nuts chasing numbers

 

[thatmanMIKEson]

Mine isn’t highest after feeding - that’s when it starts to come down. It continues its downward trend during the day until night where it seems to almost bottom out and then spikes at around 4 am. After that it remains high until feeding time and then seems to come down after.

I'm just looking, but its strange in the graph that the spike up in N03 at almost the exact same time there is a downward spike in p04, around or on the 21st

 

[Forty-Two]

I'm just looking, but its strange in the graph that the spike up in N03 at almost the exact same time there is a downward spike in p04, around or on the 21st

I agree it is interesting

 

[Forty-Two]

That's interesting.

I was surprised when I installed automatic Alk measurement how much that bounced around over 24 hours, so I suppose the same must be true of other parameters.

I ended up cutting back the testing schedule because I started going nuts chasing numbers

Haha ya my wife is telling me the same thing - just test twice a day 12 hours apart and that’s it.
Otherwise I think I’ll go nuts too.

However I see two issues with this -
1) if I record my PO4 as .75 at 4 am (which had been happening) but then it’s spiking to .15-.20 during the day - I better have a close watch if my corals otherwise I may not know that I’m killing them because ‘Params are fine’.

2) When we discuss our PO4 numbers - how accurate is that number? How often do reef tanks show .07 ish at one point in time but then travel up to .15 and it’s perfectly normal? Or maybe it’s not as the case may be?