Can high phosphate inhibit algae?

[Subsea]

@Garf

I am a seaweed grower for people editable seaweed & ornamental & utilitarian seaweeds for reef hobby. While I have never had to add phosphate to growout tanks, I think it comes in with the air, I do add ammonia. I do know that seaweed is a sponge & absorbs everything in the water. When I sent samples of Gracilaria Parvispora to be analyzed by a regional agriculture lab, both copper & zinc showed up as parts per million in samples yet those heavy metals did not show up in water analysis where lower detection limit was 5 parts per billion.

PS: Phosphate may come into seaweed grow-out tanks with liquid kelp that I dose along with ammonia.

 

[salty joe]

Maybe try adding some Chaetogro? Not the same thing but I had to start dosing it after 2 of my algae scrubbers stalled. I went from not growing algae to growing this every week.

Thanks but my tank is already high in zinc and sulphur and I top off boron, molybdenum and manganese using ATI as a guide.

What does 'phosphates exploded' mean and what is the number correlation?

I run both high nitrate and phosphate and have no trouble growing macroalgae. Here is what I recently exported from my refugium to my display to feed my animals. Sea Grapes, Caulerpa lentillifera.

To reference numbers last night my nitrate was 40.4 and my phosphate was 1.09 ppm.

Phosphate went from 1.75 to 2.8 mg/L in seven months. Nitrate is 175 mg/L. Somehow, the fish are doing great! Nice looking tank you have there!

I don’t think it likely that elevated phosphate deters any green algae unless you are talking above a few ppm phosphate.

Very high phosphate may contribute to precipitation of some trace elements such as iron, so make sure those are maintained.

I can't keep iron in that tank to save my life, I dose iron heavily and it's non detectable according to ATI. I was going to ask you on your chemistry forum if maybe a piece of cast iron in the overflow might help. Is 2.8 mg/L high enough to cause precipitation?

What peer review study are you referring too? Please provide link.,

https://pmc.ncbi.nlm.nih.gov/articles/PMC6193650/ IDK if it's peer reviewed but here ya go!

 

[salty joe]

It's hard to imagine how this would be true, but it's an interesting thought!

Can you share more details on why you think this? Also link or title for the study would be most welcome.

Would be interested to know your water test results, especially no3, po4, s.g., and temperature....as well as a little background on the tank where this is happening.

Maybe it was coincidence, maybe not IDK. Phosphate is 2.8 mg/L, nitrate is 175 mg/L, I keep salinity very close to 35 ppt, temp is 78-80F. Alk 11.3, calcium 496 - I need to dial back my kalk reactor.

I put live rock in 10 years ago but have had fish only 5 years. Phosphate and nitrate started getting out of hand last year. I didn't change how much I fed the tank. I think the rock and sand got saturated with phosphate and with no Chaeto, nitrates climbed in a hurry. GFO is on the way.

 

[Garf]

@salty joe I'll repost the link you supplied here, as it's within another window;

Confounding factors in algal phosphorus limitation experiments - PMC

Assessing algal nutrient limitation is critical for understanding the interaction of primary production and nutrient cycling in streams, and nutrient diffusing substrate (NDS) experiments are often used to determine limiting nutrients such as ...

pmc.ncbi.nlm.nih.gov

 

[Subsea]

@salty joe I'll repost the link you supplied here, as it's within another window;

Confounding factors in algal phosphorus limitation experiments - PMC

Assessing algal nutrient limitation is critical for understanding the interaction of primary production and nutrient cycling in streams, and nutrient diffusing substrate (NDS) experiments are often used to determine limiting nutrients such as ...

pmc.ncbi.nlm.nih.gov

This article is dealing with fresh water streams and algae. I don’t see the application.

First paragraph in the introduction showed they considered municipal waste water effluent:
As a former waste water superintendent I know about bugs (activated sludge) and algae.

Introduction​

Benthic algal production provides an important energy source to higher trophic levels [1], and in low productivity streams, growth of macroinvertebrate and fish grazers may be limited by the availability of algal food resources [2]. Freshwater algal growth is often limited by the availability of nitrogen (N), phosphorus (P), or both nutrients [3, 4], but human activities are increasing N and P inputs to streams via sources such as wastewater treatment effluent, agricultural runoff, and atmospheric N deposition [5]. These excess nutrients may result in harmful levels of algal biomass that degrade ecological habitat [5], stream aesthetics [6], and drinking water quality [5]. Identifying nutrients that limit algal productivity in individual stream reaches can inform stream management plans that promote human and ecosystem health.

 

[mcarroll]

@salty joe I'll repost the link you supplied here, as it's within another window;

Confounding factors in algal phosphorus limitation experiments - PMC

Assessing algal nutrient limitation is critical for understanding the interaction of primary production and nutrient cycling in streams, and nutrient diffusing substrate (NDS) experiments are often used to determine limiting nutrients such as ...

pmc.ncbi.nlm.nih.gov

So they were actually looking for explanations of errors in their testing procedure using NDS – "nutrient diffusing mediums" to grow algae in streams. It appeared that elevated P was causing low algae growth in a statistically significant amount of tests being done with NDS (>10% i think) and they thought it was an artifact, but didn't fullly understand it.

They do cite a few articles (example) that "support P-toxicity" but they seem to be all theory and just using Redfield comparisons to make assertions. Some theories that certain sources of P could be altering the medium compared to others.

It all related to this NDS medium (agar, maybe) so I wonder if this may not relate at all to natural systems?

 

[salty joe]

I'm grasping at straws trying to figure out why I can't grow Chaeto anymore, so I searched 'high phosphate inhibit algae'. You are probably right that it's not relevant.

 

[Subsea]

I'm grasping at straws trying to figure out why I can't grow Chaeto anymore, so I searched 'high phosphate inhibit algae'. You are probably right that it's not relevant.

Chaeto was never a favorite of mine. With those high numbers for P & N, I would be looking at trace minerals. Have you considered a turf algae scrubber.

 

[salty joe]

For a few months after the Chaeto crashed, I grew hair algae. Now not even hair algae grows. I've tried 3 different lights. Here is what ATI calls minor elements. I topped off molybdenum and manganese and have dosed iron heavily - twice a week - yet iron is non detectable.


Minor elements

Li
Lithium
513.4 µg/l
Ideal value: 166.4 µg/l
ABOVE NORMAL
Attention

Si
Silicon
230.6 µg/l
Ideal value: 97.86 µg/l
NORMAL
Near nature

I
Iodine
119.4 µg/l
Ideal value: 63.61 µg/l
ABOVE NORMAL
Attention

Ba
Barium
3.24 µg/l
Ideal value: 9.79 µg/l
BELOW NORMAL
Attention

Mo
Molybdenum
4.50 µg/l
Ideal value: 11.74 µg/l
BELOW NORMAL
Attention

Ni
Nickel
Not detectable
Ideal value: 0.49 µg/l
NORMAL
Near nature

Mn
Manganese
Not detectable
Ideal value: 0.98 µg/l
BELOW NORMAL
Attention

As
Arsenic
Not detectable
Ideal value: 0.49 µg/l
NORMAL
Near nature

Be
Beryllium
Not detectable
Ideal value: 0.10 µg/l
NORMAL
Near nature

Cr
Chrome
Not detectable
Ideal value: 0.49 µg/l
NORMAL
Near nature

Co
Cobalt
Not detectable
Ideal value: 0.10 µg/l
NORMAL
Near nature

Fe
Iron
Not detectable
Ideal value: 0.49 µg/l
BELOW NORMAL
Attention

Cu
Copper
Not detectable
Ideal value: 0.49 µg/l
NORMAL
Near nature
Se

Selenium
Not detectable
Ideal value: 0.49 µg/l
NORMAL
Near nature

Ag
Silver
Not detectable
Ideal value: 0.10 µg/l
NORMAL
Near nature

V
Vanadium
2.83 µg/l
Ideal value: 1.47 µg/l
NORMAL
Near nature

Zn
Zinc
6.19 µg/l
Ideal value: 1.96 µg/l
ABOVE NORMAL
Attention

Sn
Tin
Not detectable
Ideal value: 0.49 µg/l
NORMAL
Near nature

 

[Randy Holmes-Farley]

I'm grasping at straws trying to figure out why I can't grow Chaeto anymore, so I searched 'high phosphate inhibit algae'. You are probably right that it's not relevant.

Lack of adequate trace elements is not possible?
Seems obvious with your data.

 

[salty joe]

Would trace elements be less or different than what ATI calls minor elements?

 

[Randy Holmes-Farley]

Randy,
Is 0.215% the same as 2,150 ppm.

Yes, but again, that’s not a value in the water. I can’t see it a useful number in this context.

 

[Randy Holmes-Farley]

Would trace elements be less or different than what ATI calls minor elements?

iron is undetectable. It might be zero. Same with many more essential elements.

You need a better test if you really want to quantify low level trace elements. They say normal, since that test cannot detect natural levels, but recognize that you certainly may have too little.

 

[Randy Holmes-Farley]

I also pointed out that excessive phosphate may precipitate some trace elements. Dosing chelated forms may help. Ferrous gluconate, for example.

What does dosing heavily mean? Seems insufficient.

 

[salty joe]

I dissolved 3.58 grams Fergon tablets in 500 mL water. I figured 1 mL in 800 gallons would boost iron by 0.12ug/L. I've been dosing 1 mL of that solution twice a week. There's some sediment in that bottle even though I've shaken the heck out of it several times.

Can you recommend what water test I should use?

 

[EnterName]

I dissolved 3.58 grams Fergon tablets in 500 mL water. I figured 1 mL in 800 gallons would boost iron by 0.12ug/L. I've been dosing 1 mL of that solution twice a week. There's some sediment in that bottle even though I've shaken the heck out of it several times.

Can you recommend what water test I should use?

The current ATI ICP-MS test (a bit more expensive than the ATI ICP-OES test) can detect significantly lower levels of many elements. For iron (Fe) it goes down to 0.20μg/L which is sufficient to check if you are near the proposed normal levels of 0.50μg/L.

I don't know if Fergon tablets are suitable for iron dosing in a reef tank, but they contain "microcrystalline cellulose" and "crospovidone". Both are practically insoluble in water. Maybe that is causing the sediment.

Not all tablets are perfectly mixed, which means if you had to cut off a piece to get to your 3.58g you might have gotten a piece which doesn't contain much iron at all.

 

[salty joe]

Oh, no kidding I looked at the ATI site and only saw the ICP-OES. I'll check that out.

I completely ground up several entire tablets of Fergon and only used 3.58 grams.

 

[KrisReef]

I hope you get this Ironed out.

Pretty interesting thread.

 

[Randy Holmes-Farley]

It may not be iron that is limiting, or it may be. Oceamo does a good ICP-MS test.

Bear in mind, however, that a number by ICP for many trace elements says little about its bioavailability since ICP does not distinguish chemical forms.

I'd recommend a full cocktail of additives, such as Tropic Marin A and K.

 

[salty joe]

OK, thanks. I'll get an ICP-MS test and meanwhile use and learn how to regenerate GFO as soon as it gets here.

Since very little algae is growing, could the iron I've been adding go anywhere besides precipitating? Would my high alk of 11.3 make precipitating iron more likely?

The issue I have with the cocktail approach is my levels of zinc, lithium and other stuff are already too high.

Good to know there is a more high powered ICP! Thank you!