# Wanted: Phosphate for Green Spot - in Plain English



## DarkCobra (Jun 22, 2004)

funcrew said:


> Hi - I read several of the threads on phosphate dosing, but the answers were at a level above my head. Could someone direct me to a "basics" thread or answer:


Hi Funcrew. I can simplify for you.



funcrew said:


> 1. My "old school" understanding was that algae resulted in high nitrate and/or phosphate levels. Adding phosphate seems very counter-intuitive. Is this now standard procedure for GSA?


Yes, it's now pretty much standard procedure. And yes, it's counterintuitive if you were ever exposed to the "old school" of just a few years ago. 

This may be more than you want/need right now, but here's a different explanation of the new school theory.

Algae is more efficient at collecting nutrients than plants. You cannot starve the algae without also starving, or at least causing deficiencies in, your plants.

However, new algae spores don't germinate and grow unless they know conditions are right for algae growth, and they watch ammonia levels to determine that. So ammonia is the new Tank Enemy #1.

Fish and other critters constantly produce it, plants and biofilter constantly use it. In a normally functioning tank, ammonia is undetectable with a test kit, with levels floating somewhere in the parts-per-billion (ppb). But the algae spores can still detect and respond to even those low levels.

So the idea is, by having a tank full of healthy, well-fed, and fast-growing plants, they can soak up the ammonia in the tank a little quicker. The difference is only a few ppb, but that's enough to slow, or even nearly stop new algae growth.



funcrew said:


> 2. How to test Phophate level - will my standard phosphate test kit give good enough results? Or should I start dosing and see if the GSA goes away?


The test kit gives good enough results, within a ppm or two. I suggest you use the test kit, at least at first, to verify that you're dosing the amount you think you are. Some people will disagree with me on this, but I'm going to tell you that a large overdose can cause algae problems. Been there, done that..

Realistically, the algae almost never just "goes away". New algae growth slows or stops, but the GSA that is there will remain there until you remove it.



funcrew said:


> 3. What product(s) to use? The forum posts use chemical formulas, I don't know how to buy that stuff. Also, how to figure out desired PPM for the recommended product.Thanks!


Greg Watson sells every chemical you could possibly need. I was weaned into this hobby using his chems.  You can also add phosphate with a Fleet Enema, which is nothing but a liquid phosphate solution, and is available in any supermarket.


----------



## Hoppy (Dec 24, 2005)

To figure how much of a chemical to add go to http://www.csd.net/~cgadd/aqua/art_plant_dosage_calc.htm
For KH2PO4, mono potassium phosphate, from that website, 
PO4 - Phosphate 69.8% - KH2 30.2% 
That means to get 1 gram of phosphate takes 1/.698 or 1.43 grams of KH2PO4. nd, from the same site 1 teaspoon of KH2PO4 is 4.8 grams. So 1.43 grams of KH2PO2 = 1.43/4.8=.24 tsp or about 1 quarter tsp. 25 gallons of water is about 4000X25=100000 grams of water. So 1/4 tsp of KH2PO4 in 25 gallons of water gives 1/100000 times 1000000= 10 ppm of phosphate. You can just as easily figure dosing for other ferts.


----------



## Stan the Man (Dec 12, 2005)

Hey DarkCobra,

That was a fantastic summary, and put into simple terms. Good job!:thumbsup:


----------



## funcrew (Aug 3, 2005)

OK - that's just what I was looking for. What PPM concentration of Phosphate should I try to maintain, and does the concentration of Nitrate present have any bearing on desired Phosphate level?


----------



## DarkCobra (Jun 22, 2004)

funcrew said:


> OK - that's just what I was looking for. What PPM concentration of Phosphate should I try to maintain, and does the concentration of Nitrate present have any bearing on desired Phosphate level?


Depends on who you ask.  I'd recommend 2ppm phosphate.

Some people say there is a desired ratio between nitrate and phosphate, but whether that's true is open to debate.

One more thing - excessive lighting periods can grow GSA. If the phosphate doesn't work, cut your lighting interval by 20% and see how it affects the growth of new GSA.


----------



## Stan the Man (Dec 12, 2005)

funcrew said:


> OK - that's just what I was looking for. What PPM concentration of Phosphate should I try to maintain, and does the concentration of Nitrate present have any bearing on desired Phosphate level?


As well, the ratio of nitrate to phosphate is important to consider. An optimal ratio of 10:1 is often quoted; e.g., 10 ppm nitrate to 1 ppm of phosphate, or 5 ppm nitrate to 0.5 ppm of phosphate. This is based on the Redfield ratio, where a ratio less than 10 favours blue-green algae, and greater than 22 favours green algae. There's lots of great information about the Redfield ratio, as well as an excellent Redfield calculator at:
http://www.xs4all.nl/~buddendo/index.html


----------



## funcrew (Aug 3, 2005)

Great - Thanks! I'll make the changes and report the results.


----------



## plantbrain (Dec 15, 2003)

Stan the Man said:


> As well, the ratio of nitrate to phosphate is important to consider. An optimal ratio of 10:1 is often quoted; e.g., 10 ppm nitrate to 1 ppm of phosphate, or 5 ppm nitrate to 0.5 ppm of phosphate. This is based on the Redfield ratio, where a ratio less than 10 favours blue-green algae, and greater than 22 favours green algae. There's lots of great information about the Redfield ratio, as well as an excellent Redfield calculator at:
> http://www.xs4all.nl/~buddendo/index.html


Yea, except the entire premise is incorrect.

BTW Good summary DC.

That's how it works, we repay our help from others, by helping the new folks.
You also get much better at your own skills and knowledge in doing so. 

Careful with those cheap test kits though, even the best Lamotte (60$) is accurate to 1-5ppm of NO3 at best.

I like 2-3ppm of PO4, but anything in the 1-3ppm a week range is good.

Regards, 
Tom Barr

www.BarrReport.com


----------



## wapfish (Oct 14, 2005)

DarkCobra said:


> This may be more than you want/need right now, but here's a different explanation of the new school theory.
> 
> Algae is more efficient at collecting nutrients than plants. You cannot starve the algae without also starving, or at least causing deficiencies in, your plants.
> 
> ...


Wow! 

I thought this business about low level ammonia-sensing -> spore germination -> algae (in the absence of sufficient plant mass to suck up the ammonia) was just a hypothesis Tom was floating. Interesting, true, but is it really generally accepted as the "new school"?


----------



## Stan the Man (Dec 12, 2005)

plantbrain said:


> Yea, except the entire premise is incorrect.
> 
> BTW Good summary DC.
> 
> ...


Hi Tom,

I'm just curious as to why the premise of the Redfield ratio is incorrect. I've been trying to gleen helpful advice through the forums / internet, such as your ammonia hypothesis, which has worked very well. From what I've read so far, the Redfield ratio sounds reasonable.

Thanks.


----------



## wapfish (Oct 14, 2005)

DarkCobra said:


> However, new algae spores don't germinate and grow unless they know conditions are right for algae growth, and they watch ammonia levels to determine that. So ammonia is the new Tank Enemy #1.
> 
> Fish and other critters constantly produce it, plants and biofilter constantly use it. In a normally functioning tank, ammonia is undetectable with a test kit, with levels floating somewhere in the parts-per-billion (ppb). But the algae spores can still detect and respond to even those low levels.
> 
> So the idea is, by having a tank full of healthy, well-fed, and fast-growing plants, they can soak up the ammonia in the tank a little quicker. The difference is only a few ppb, but that's enough to slow, or even nearly stop new algae growth.


You realize that whenever you do a water change and have chloramine in your water, you are dosing with a substantial amount of ammonia that is biologically available to the biofilter (eg Prime = ammonia complexed with sulfites), and would presumably (?) also be available to both plants and algae? Here where I live, chloramine levels are around 2.5 ppm, so with a 50% water change, that's a fair dose of ammonia, well above the ppb level. Yet this doesn't seem to induce algae or make it any worse. In fact, it actually seems to help in holding algae back for a bit.


----------



## DarkCobra (Jun 22, 2004)

wapfish said:


> I thought this business about low level ammonia-sensing -> spore germination -> algae (in the absence of sufficient plant mass to suck up the ammonia) was just a hypothesis Tom was floating. Interesting, true, but is it really generally accepted as the "new school"?


LOL! In the context of Funcrew's question, it is the "new school", by contrast to phosphate limiting which he stated as the "old school". That was a personalized answer, meant to be understandable to the person to whom it was addressed. If you're interpreting it as a statement about the general acceptance of Barr's hypothesis, you've misinterpreted it. 



wapfish said:


> You realize that whenever you do a water change and have chloramine in your water, you are dosing with a substantial amount of ammonia that is biologically available to the biofilter (eg Prime = ammonia complexed with sulfites), and would presumably (?) also be available to both plants and algae? Here where I live, chloramine levels are around 2.5 ppm, so with a 50% water change, that's a fair dose of ammonia, well above the ppb level. Yet this doesn't seem to induce algae or make it any worse. In fact, it actually seems to help in holding algae back for a bit.


Yeah, I've been wondering about that.

The key word is "presumably".  I've been looking for information to help me understand exactly how this works.

So far, I've found a description of the chemical reaction that takes place between an anti-chloramine agent and the chlorine/ammonia. And it's obvious enough that it does at least detoxify the ammonia, otherwise we'd have a bunch of dead fish!

But I haven't found any information on how the biofilter is still able to process the new, altered form of ammonia. Or whether plants and algae can do the same.

If it effectively hides the ammonia from algae, it offers an explanation why a water change holds back algae for a bit. We use anti-chloramine agents *in excess*. No one bothers to measure out the exact amount they need to cancel the chloramine in their water supply; and that's a good thing, since the chloramine can fluctuate. Whatever is left over will remain in the tank, continuing to bind up ammonia. Perhaps this is an easy, if a bit irresponsible, way to an algae free tank - simply add Prime every day!

Or there could be another explanation. I've seen a couple of research papers studying the effects of phosphates in waterways. Both stated that excess phosphates do not cause an algae bloom, unless other pollutants are present. Frustratingly, they don't mention what the "pollutants" are. But it makes me wonder if ammonia is just one of many organic byproducts of fish metabolism that cause algae growth, that are removed with a water change, and are not replenished by tapwater or by our inorganic fertilizers.

Whatever the case is, there is one thing obvious to me. In our planted tanks, everything needed for algae growth is present in abundance. Light, CO2, N/P/K, every trace element. Algae should be completely choking our tanks. Yet most of the time, it does not. There is obviously some limiting factor specific to algae other than the raw energy and raw elements.

Enough rambling for now.


----------



## plantbrain (Dec 15, 2003)

wapfish said:


> Wow!
> 
> I thought this business about low level ammonia-sensing -> spore germination -> algae (in the absence of sufficient plant mass to suck up the ammonia) was just a hypothesis Tom was floating. Interesting, true, but is it really generally accepted as the "new school"?


It is just a notion, but it explains the hypothesis based on our obnservations better than any other. It applies equally to non carbon enriched systems as well as CO2/Excel enrichment. 

Take a stable well run plant tank:

We can add NH4=> algae
We can add NO3=> no algae.

I base my hypothesis on observations (not just random stuff that sounds cool or monkey's flying out of my butt

1. We make observations, we test to see if we can repeat/predict these observations, then go about trying to figure out why things are that way and hopefully come to a conclusion.

The NH4 vs the NO3 approach shows one possible mechansim. 
It's repeatable. We normally add lots of NO3, no algae, we add too many fish(excess NH4 loading to a tank)=> algae. Some claimed it was the PO4 from the fish, so we add PO4=> no algae.

What is left?
NH4.

But some algae seem to be induced by variation in CO2.
Some are supressed(new spore germination) by high levels of CO2.
Algae species have specialized germination conditions. 

We know what most are by testing. 
Once the adults are there, they are able to survive with reserves, spores have no such reserve. 

By placing a large healthy plant that is several weeks old vs an alga spore, we give the planbt a much greater leg up on the NH4 uptake and light vs a seed vs an algae spore. 

Regards, 
Tom Barr


----------



## plantbrain (Dec 15, 2003)

Stan the Man said:


> Hi Tom,
> 
> I'm just curious as to why the premise of the Redfield ratio is incorrect. I've been trying to gleen helpful advice through the forums / internet, such as your ammonia hypothesis, which has worked very well. From what I've read so far, the Redfield ratio sounds reasonable.
> 
> Thanks.


Simple, you can try it and see.
I've had PO4 levels at 1ppm and NO3 at 5ppm for a few years, then had NO3 at 20ppm and the same PO4. Then tried 30ppm and 2-3 ppm, others do well with small dosings of PO4, say .5ppm or less and higher NO3, say 10-15ppm.

As long as they are not limiting , the concept of a ratio offers you nothing in terms of plant health/growth, nor algae.

Adding more PO4 helps supress GSA, same with BGA for NO3.
Bt the ratio is not critical, it is when limiting situations may occur in natural systems where there is no dosing being added, but not with argicultural crops unless they are very high/disproportionate to the point of toxicity.

Where ratios help: efficent use of fertilizers depending on soil or tank conditions.

If you have high PO4 in the tap etc, then using a fertilizer mix w/o PO4 will be useful and save some cost.

But this applies mainly to huge crop systems, the ferts for us are very cheap and offers no economic gain for us.

When you discuss the Redfiled ratio, it is *atomic ratios, not atomic mass*.

So for each P atom there are 16 N atoms. 
It's not 14 g/mol n x 16 and 30.97 g/mol P, that mass ratio gives you a ratio of about 7:1 N. 

Something folks often misunderstand.
They confuse *mass and atomic *numbers.
This throws you off by a factor of over 2x.

So ratios can mix you up if they are misapplied/misunderstood.
7:1 N is a decent ratio.

Check to see if they made this mistake.
Many do.

But it will not save you from algae in anyway. 

Regards, 
Tom Barr

www.BarrReport.com


----------



## plantbrain (Dec 15, 2003)

wapfish said:


> You realize that whenever you do a water change and have chloramine in your water, you are dosing with a substantial amount of ammonia that is biologically available to the biofilter (eg Prime = ammonia complexed with sulfites), and would presumably (?) also be available to both plants and algae? Here where I live, chloramine levels are around 2.5 ppm, so with a 50% water change, that's a fair dose of ammonia, well above the ppb level. Yet this doesn't seem to induce algae or make it any worse. In fact, it actually seems to help in holding algae back for a bit.


But it is bound, not freely available inorganic. The form is important.
Regards, 
Tom Barr


----------



## plantbrain (Dec 15, 2003)

I will say this, weed science approachs to prevent weeds pre and post emergence really shows when it's important to keep on algae control(think weed control here) 

There is about a 1-4 week window where you need to keep up on things and then the tank evens out. Adding a high density of plants(crops) in good shape is a critical element here.

Providing the plants with good growing conditions immediately also helps.
Once a tank is over the hump, it is very stable and excludes the algae.

regards, 
Tom Barr


----------

