Sudden spike in Phosphate after water change -- caused by cyano removal?

[mike550]

Over the past year or so, my phosphate has averaged around 0.03 (nitrates around 8). Two days ago I did a 15% water change and the next day my phosphate spiked to 0.19 (measured using Hanna ULR Phosphorous). I measured again today, and phosphates are around 0.17. In terms of maintenance I've been having a green cyano issue so I vacuumed the cyano off the rocks when I did the water change. I tested the "fresh" saltwater that I used for the water change, and phosphate was 0. And eveything else was "normal".

Can removing cyano cause a spike in phosphate?

Parameters:
Salinity: 33
Alk: 8.4
Phos: 0.17
NO3: 8
Ca: 460
Mg: 1400

Thanks in advance!

 

[salt2salt]

yep

 

[F i s h y]

yep

2nd this...
By removing the cyano, you have essentially removed the organism responsible for export...

 

[mike550]

2nd this...
By removing the cyano, you have essentially removed the organism responsible for export...

Thanks @Fishy65 and @salt2salt So should I start using GFO to reduce phosphates?

I'd like to get to the cause of this, but not sure where to begin. For what it's worth, I'm also dosing NoPox which I know can impact phosphate and nitrate. But nitrates seem to be staying stable.

 

[F i s h y]

Thanks @Fishy65 and @salt2salt So should I start using GFO to reduce phosphates?

I'd like to get to the cause of this, but not sure where to begin. For what it's worth, I'm also dosing NoPox which I know can impact phosphate and nitrate. But nitrates seem to be staying stable.

Need more information about your setup. I like to use more natural means of nutrients export like a refugium full of macros or chaeto... removing organics with a skimmer can also help. But depending on what kind of bioload you have, and the types of organisms will also influence your decision. For instance... I run this 40B with no sump no skimmer, feed heavy (both coral and fish), and do a once a week 5 gallon water change...

I dont recommend this setup for most people

 

[mike550]

Need more information about your setup. I like to use more natural means of nutrients export like a refugium full of macros or chaeto... removing organics with a skimmer can also help. But depending on what kind of bioload you have, and the types of organisms will also influence your decision. For instance... I run this 40B with no sump no skimmer, feed heavy (both coral and fish), and do a once a week 5 gallon water change...

Fair enough. 120G mixed reef tank that's about a year old (but not too many corals), with eight fish, a couple of BTA, and CUC. I think it's a light bioload, and I'm a "medium" feeder primarily using Rod's frozen. Not running a refugium, but running a KLIR-7 for mechanical filtration and a skimmer. Dosing ESV two part and NoPox.

Typically do 15 or 20G weekly water changes.

 

[blasterman]

Need more information about your setup. I like to use more natural means of nutrients export like a refugium full of macros or chaeto... removing organics with a skimmer can also help. But depending on what kind of bioload you have, and the types of organisms will also influence your decision. For instance... I run this 40B with no sump no skimmer, feed heavy (both coral and fish), and do a once a week 5 gallon water change...

I dont recommend this setup for most people

This is really similiar to my 20L, except I have more 'junk' SPS like blue digis and poc's growing like wild fire.

I took my skimmer offline a few months ago because I was tired of nitrate running in negative digits. I do run ozone, but only a few hours at night and only long enough to remove any color cast to the water, which is a rough indication of DOCs. I will take this combination over a skimmer any day. No water changes in 6months. I darn near have to run a constant drip of phosphate to keep it even detectable.

Which brings me to the point: I've seen some studies on cyano and related bacteria and heavy evidence that they have different dominant strains capable of fixing either nitrate or phosphate. This would also explain why some of us have issues with keeping nitrate or phosphate stable because it depends on what strain has become dominant. If bacteria can evolve quickly to beat antibiotics they can sure as heck adapt to different nutrient sources.

 

[Randy Holmes-Farley]

Which brings me to the point: I've seen some studies on cyano and related bacteria and heavy evidence that they have different dominant strains capable of fixing either nitrate or phosphate. This would also explain why some of us have issues with keeping nitrate or phosphate stable because it depends on what strain has become dominant. If bacteria can evolve quickly to beat antibiotics they can sure as heck adapt to different nutrient sources.

Can't all photosynthetic organisms "fix" (use) phosphate?

I agree that cyano can theoretically fix N2 from the air, reducing their need for other N sources, but how much that, happens in a reef aquarium, I do not know.

 

[Dan_P]

Over the past year or so, my phosphate has averaged around 0.03 (nitrates around 8). Two days ago I did a 15% water change and the next day my phosphate spiked to 0.19 (measured using Hanna ULR Phosphorous). I measured again today, and phosphates are around 0.17. In terms of maintenance I've been having a green cyano issue so I vacuumed the cyano off the rocks when I did the water change. I tested the "fresh" saltwater that I used for the water change, and phosphate was 0. And eveything else was "normal".

Can removing cyano cause a spike in phosphate?

Parameters:
Salinity: 33
Alk: 8.4
Phos: 0.17
NO3: 8
Ca: 460
Mg: 1400

Thanks in advance!

How many days before the PO4 spike did you measure the PO4?

 

[mike550]

How many days before the PO4 spike did you measure the PO4?

@Dan_P Here are my PO4 measurements. Dec 30 was the last measurement before the water change.

Sunday, Dec 27 -- PO4 0.01
Wednesday, Dec 30 -- PO4 = 0.1
Saturday, Jan 2 (Water Change)
Sunday, Jan 3 -- PO4 = 0.19
Monday, Jan 4 -- PO4 = 0.17

In fairness, PO4 started increasing before the water change, but prior to Dec 30, my PO4 was always running between 0.01 - 0.07 through December.

 

[Dan_P]

@Dan_P Here are my PO4 measurements. Dec 30 was the last measurement before the water change.

Sunday, Dec 27 -- PO4 0.01
Wednesday, Dec 30 -- PO4 = 0.1
Saturday, Jan 2 (Water Change)
Sunday, Jan 3 -- PO4 = 0.19
Monday, Jan 4 -- PO4 = 0.17

In fairness, PO4 started increasing before the water change, but prior to Dec 30, my PO4 was always running between 0.01 - 0.07 through December.

Thanks for the data. I was thinking that harvesting cyanobacteria could not increase PO4. I just could not think of any explanation short of a conspiracy theory

Yeah this is a mystery, though I would start with “what is going into the aquarium”. A distant second choice for investigation is “what stopped working”. My PO4 increases seem to be related to my generous feeding.

 

[mike550]

Thanks for the data. I was thinking that harvesting cyanobacteria could not increase PO4. I just could not think of any explanation short of a conspiracy theory

Yeah this is a mystery, though I would start with “what is going into the aquarium”. A distant second choice for investigation is “what stopped working”. My PO4 increases seem to be related to my generous feeding.

Thanks for your thoughts on this. I've removed cyano before and never saw this. So to your point, I'm trying to figure out what else may have changed.

 

[Galaxy reefer]

Just saw this post today. Not sure what its worth but I was having the same issue. I traced it back to my source of ro water. For some reason my system was testing at higher than what was in my tank. The top off water and water changes continued to increase my levels. Once I figured it out no more cyano or increased levels of phosphate. Might be worth looking into.