Head Scratcher.. Nitrates But No Phosphates

[HighestOlive]

I have been having a bit of trouble with my SPS STN'ing recently. At first I thought it was my pellet reactor stripping all of the nitrate and phosphate out of my tank leaving practically zero nutrients. So I pulled the pellet reactor and initially things looked like they were starting to turn around. and then some of the acros started STN'ing again. Here are the results of the testing that I just performed:

SG: 1.024
Temp: 77.2oF
pH 8.2
Alk: 8.3 dkh (Hanna Checker)
Ca: 445 ppm (Hanna Checker)
Mg: 1270 ppm (Salifert)
Nitrate 4 ppm (Red Sea Pro)
Phosphate 0.00 ppm (Milwaukee low range).

Does anyone else find it a bit odd that I have a pretty decent level of Nitrates but zero detectable phosphates? I feed fairly heavily as well. Should I be concerned that I can't detect phosphate or could this imbalance between nitrate and phosphate be causing some of the STN?

Some additional information:

I have tested my RO for chlorine and chloramines, both 0.
I am reading 1 ppm on my TDS meter on my RO Unit and have ordered new media to fix that.
Results of ICP testing that was performed 2 weeks ago (nothing stands out to me, CA was a bit high due to an over dose and has since fallen with water changes and not dosing).
Aluminum 0.11 ppm
Arsenic 0.01 ppm
Boron 2.44 ppm
Barium 0 .01 ppm
Beryllium 0 ppm
Bromine 87.9 ppm
Calcium 621.5 ppm
Cadmium 0 ppm
Cerium < 0.01 ppm
Chlorine 23683.82 ppm
Cobalt 41.28 ppm
Chromium 0.02 ppm
Copper 0 ppm
Iron 0 ppm
Gallium 0.95 ppm
Iodine 0.01 ppm
Potassium 452.25 ppm
Lanthanum 0.02 ppm
Lithium 0.62 ppm
Magnesium 1306.09 ppm
Manganese 0 ppm
Molybdenum 0.04 ppm
Sodium 9798.72 ppm
Nickel 0.06 ppm
Phosphorus 0.08 ppm
Lead < 0.01 ppm
Rubidium <0.01 ppm
Sulfur 332.51 ppm
Antimony 0 ppm
Selenium 0.01 ppm
Silicon <0.01 ppm
Tin 0.04 ppm
Strontium 6.83 ppm
Titanium 0 ppm
Thallium <0.01 ppm
Uranium 0.05 ppm
Vanadium 0.01 ppm
Tungsten 0 ppm
Zinc 0 ppm

Tank is a 90 gallon display that has been running since February, lite with 4 radion Gen 4 XR15 pros. Water movement is provided by 2 MP40 that alternate between reef crest and nutrient export. Rock work was moved from a previous tank that started to leak, but DSB is new for the most part (some of the old sand was mixed in to seed. Goes without saying there is also a skimmer.

Vortechs have been check to ensure there is no rust.
I haven't been running carbon, but I just started running it again today to see if there an unknown organic was causing issues.

I don't see any sign that this is an SPS pest. It really seems like a chemistry issue that I can't pinpoint. Any help that people can provide would be great. I would be happy to answer any additional questions.

 

[Bananafish]

Is that Chlorine correct? 23683.82 sounds high

Sent from my Moto G (5) Plus using Tapatalk

 

[bertoni]

Results like that are fairly common. I probably would back off on the pellets, to see whether they might be removing too much phosphorus from the water column. Some tanks seem to have problems due to nutrient control techniques. It's also possible to dose a bit of phosphate. There are food-grade sodium triphosphate products available on Amazon that will work, for example.

 

[HighestOlive]

Here is an example

 

[HighestOlive]

Is that Chlorine correct? 23683.82 sounds high

That is the Chlorine level that the test read. According to the results water from Hawaii tests at 20453.92 and water from Florida tests at 19283.07. So yes that level is high than those location but is it that much high I don't really know. That being said that level was what prompted me to test for chlorine and chloramine in my RO. Is there really a way to lower that other than water changes? Or even really to test for total chlorine besides doing an IPC analysis.

 

[HighestOlive]

Results like that are fairly common. I probably would back off on the pellets, to see whether they might be removing too much phosphorus from the water column. Some tanks seem to have problems due to nutrient control techniques. It's also possible to dose a bit of phosphate. There are food-grade sodium triphosphate products available on Amazon that will work, for example.

Totally pulled the pellets. I am halfway considering putting them back on and lowering the total amount big time. I was doing a full "dose" before (since I started the tank). I would probably cut that down 10x.

Would there be a benefit to adding some phosphate? I was considering trying to pick up something to dose a bit if it made sense.

 

[Dan_P]

The ICP phosphorous level of 0.08 ppm corresponds to 0.25 ppm phosphate. Phosphorous can be part of organic molecules or polyphosphate in the water or be part of microorganisms in the water sample. All of these are not detected by a phosphate test kit though. Not sure though what fraction of these would be available to coral. In any case, you have definitely not stripped out the phosphorous in the aquarium, even though phosphate is undetectable.

Before focusing on the phosphate level as an issue, confirm the phosphate test is working by testing a standard. Also, manufacturers rarely if ever discuss the fact that the limit of detection of their tests is above 0 PPM which means that when your test indicates zero, there could still be 0.01 or 0.02 ppm phosphate.

 

[HighestOlive]

Thanks for that bit of info Dan. In the past I have never really thought about the relationship between phosphorus and phosphate and how that impacts our tanks. Probably since we all normally.

Based on the literature that comes with the Milwaukee low range meter I use the range they claim is 0.00 to 2.50 mg/L, with a prescision of +/- 0.04 mg/L. Based on their claimed range alone (and the number of significant digits they claim) I would expect the meter to be able to detect well below 0 ppm. i would in fact expect that it should be able to test down to 0.01 ppm other wise it would not make sense for them to claim that number of sig figs. I will grant that they don't provide a limit of quantitation or a limit of detection in their literature so these are just somewhat educated assumptions. All the same I am going to check my meter and make sure it is working porperly.

Meter aside, could high levels of phosphate or phosphorus be causing the issuses that are being observed. Typical high phosphates are associated with browning out, stunted coral growth and algae growth. I however am not seeing impact on color and the corals are STNing (which in turn mean they aren't growing). I am also seeing just a little bit of algae growth over the past week but I think that was somewhat related to my skimmer adjustment and the fact that it wasn't pulling much while I was away on vacation (but to be fair this could also be relate to a phosphate/phosphorus issue).

 

[HighestOlive]

Also want to add that coralline growth does not appear to be affected.

 

[tmz]

A few things:

sg at 1.024 is marginally low: 1.026 is better ,IMO;

Mg is ok at 1280; though I prerfer it around 1400ppm;

New sand often binds PO4 for a time ; it also takes a while for denitrifying bacteria to colonize it;

lighting intensity could be part of the problem.

1 tds is fine for an ROunit; it's bad for an RO/ DI unit.

Biopellets are complex carbohydrates with long degradation pathways and a plethora of by products. Some of which may prove harmful.

I prefer simpler soluble organics( ethanol and acetic acid/ aka vokda and vinegar) which are easier to dose at a constant level vs a reactor .

 

[HighestOlive]

Thanks for the comments TMZ. I agree with you on the SG. I will be working to bring that up. Also the mag is a tad on the lot side as well but neither of this things would cause me to think that SPS should be peeling.

I tested my PAR a little while back and it was a bit low. So I was increasing it. Yesterday I checked it again and it was at 178 though most of the tank. Again still on the low side, and you expect to see SPS browning a little bit and not bleaching and peeling.

It is a RODI unit. I guess I didn't really specify in my original post. So yeah that all needs to be changed. But 1 TDS is one TDS regardless whether is is RO vs RODI would still cause that same damage if that was the issue.

Right now the pellet reactor is totally offline and I don't want to carbon dose at this time. Until I get things sorted out.

 

[bertoni]

Chlorine should be present at about 20,000 ppm in seawater. The level reported is a bit high, but possibly within the error limits of the testing methodology. I wouldn't worry much about it, yet. We don't have good error bounds for the ICP available to most of hobbyists, anyway. I'm not sure who did these measurements.

 

[HighestOlive]

The testing was preform by IPC Analysis dot com.

 

[bertoni]

Interesting. What did they charge you? Did you get the "scan"?

 

[HighestOlive]

Testing costs $30. You can buy the test kit (sample vial and mailer) on amazon and then you mail them.

 

[bertoni]

I wouldn't place too much emphasis on the results of the tests. It's unlikely that they can be very precise at that cost. There are some articles on Triton testing accuracy, if you want some data on the subject.

 

[jason2459]

And I can say they are certainly not any more reliable then Triton. Their suggested numbers for Hawaii and Florida are misleading and unnecessary.

 

[tmz]

But 1 TDS is one TDS regardless whether is is RO vs RODI would still cause that same damage if that was the issue.

It is not the same. Some elements that have lower charges can be displaced in large quantities from di resin by elements with higher charges when the cation or or anion resin is exhausted as is the case when post di tds is greater than 0. So , as one example a release of ammonia at a concentration much higher than the post membrane level could occur.

 

[Dan_P]

Based on the literature that comes with the Milwaukee low range meter I use the range they claim is 0.00 to 2.50 mg/L, with a prescision of +/- 0.04 mg/L. Based on their claimed range alone (and the number of significant digits they claim)

Just a further thought. Roughly speaking, for a precision of +/- 0.04 ppm, a meter reading of 0 ppm means 0 +/- 0.04 ppm. This is the doubt or range of the exact level. If the vendor is being generous and the stated precision represents only 1 standard deviation (67% certainty), a better estimate is 3 standard deviations (99% certainty that the reading isn't chance or noise) or 0 +/- 0.12 ppm.

I think even if the meter is working properly, there is reasonable doubt about exactly how low the phosphate is.

 

[HighestOlive]

But 1 TDS is one TDS regardless whether is is RO vs RODI would still cause that same damage if that was the issue.

It is not the same. Some elements that have lower charges can be displaced in large quantities from di resin by elements with higher charges when the cation or or anion resin is exhausted as is the case when post di tds is greater than 0. So , as one example a release of ammonia at a concentration much higher than the post membrane level could occur.

Fair enough. Either way I have ordered new filters for my RODI system and they will be changes out soon.