Using the Redfield Ratio for balancing nutrients (algae control)

marine590622

Mod Introduction:
The following discussion spawned from this thread https://www.fishlore.com/aquariumfi...air-algae-under-control-i-have-corals.142243/

Thanks to marine590622 for raising the topic.

The information posted by marine suggests that the aquarist can balance their Nitrates and Phosphates by utilising the Redfield ratio, as a means of reducing the chances of blue-green algaes.

The concept is well known to marine/reef aquarists as a means of nutrient reduction when carbon dosing, but this approach is used to remove nutrients in the Saltwater environment (where minimal NO3O4) is desired.

I had never seen it applied to FW, and never seen it utilised as a means of balancing nutrients, where NO3O4 is required to feed the plants.

It's certainly an interesting discussion/concept.
End introduction


https://buddendo.home.xs4all.nl/aquarium/redfield_eng.htm

Read up on the redfield ratio. Once you understand the ratio messure phosphate and nitrate and you will find your redfield ratio, as you experiencing a green algae, you will either need to add phosphate, or remove nitrate to achieve a redfield ratio that does not promote the growth of algae. Simple yes? well maybe not so much the ppm measurements involved are beyound the granularity of most home test kits, but you can also look at the chart and determine which direction you would need to go to achieve a required change in you algae state.

Hope that helps.
 

marine590622

HI marine, good info - with one caveat.
To the best of my knowledge, the Redfield Ratio applies to carbon dosing (VSV, NO3O4-X, bio pellets). The link you mentioned only contains two thirds of the ratio (16:1), the ratio, as I understand is actually 106:16:1 (Carbon:NO3O4)

"In simple terms, in order to accelerate uptake of nutrient by addition of organic carbon, you need 106ppm of organic carbon to reduce 16ppm of nitrate, and you need 106 ppm of Organic carbon and 16ppm nitrate to reduce 1ppm of phosphate."

Now for DearPrudence, it is very important to identify what type of algae it is. Normal basic hair algae normally disappears on it's own by keeping some snails (Turbos for example) and very low NO3O4

If it is Bryopsis - which is often mistankingly called hair algae (they look similar) - that's a whole beast of it's own, and can be very difficult to get rid of. The best success is achieved using Kent Tech M (I think that's it) - a magnesium supplement. ONLY do this if you identify it as bryopsis, and ONLY if you have a Mg test. PS - by all reports, it's only the Kent brand that works.

The following may help you identify your algae:

I'm not necessarily opposed to the black-out concept, but before doing the black out, how long are your lights on? Reducing the photo period may help.

Ryan, I agree the original redfield ratio includes the carbon information, and is now outdated as the increased co2 levels are now indicating that much higher levels of carbon can be tied up with the same levels of phosphate and nitrate. But that is not what I am worried about as much as the sweet spot on the chart I linked to many freshwater planted folks have found they can reduce the incidence of algae in their aquariums by testing for phosphate and nitrate and then dosing one or the other to move the combined two part ratio into the sweet spot.




So lets say your phosphate where at 1 mg per litter and your nitrate was at 31 mg per litter your redfield ratio number would be 46 and you would have a high probability of having green algae.

So what to do. If you could remove nitrate without using phosphate you would want to drop you nitrate to at least 10 mg per liter which would move your redfield ration to the left resulting in a redfield ratio number of 15. a ratio where the likelyhood of either blue green or green algae is unlikely. Now with the ratio where you want it you can do a sufficiently large water change to drop your nitrate to a healthy level. Problem is how do you remove just the nitrate, you really cant, so instead you add phosphate to bring your phosphate number up to 2 mg per liter. You once again have a redfield ratio of 15 Likelyhood of algae is reduced to net to zero. and again you can do a water change and for whatever percentage of the water you leave the dilution of the nitrate and phosphate will be the same total percentage of the totals and the ratio when said and done should remain at the level of 15.

I hope that makes sense to you.
 

ryanr

Ryan, I agree the original redfield ratio includes the carbon information, and is now outdated as the increased co2 levels are now indicating that much higher levels of carbon can be tied up with the same levels of phosphate and nitrate. But that is not what I am worried about as much as the sweet spot on the chart I linked to many freshwater planted folks have found they can reduce the incidence of algae in their aquariums by testing for phosphate and nitrate and then dosing one or the other to move the combined two part ratio into the sweet spot.

Hi, yep, I understand the process (I use bio-pellets and was nitrate limited), but respectfully, your link refers to a freshwater environment. The OP is talking about a Saltwater environment - where there is minimal CO2 due to high water flows and surface agitation (CO2 doesn't last long in SW), and especially if running a skimmer injecting lots of oxygen into the water. Thus the carbon aspect of the ratio is important. For Redfield to work in SW, we need to add a carbon source (Vinegar/Vodka/Sugar or similar)

The link you provided also specifically talks about blue-green algaes in a freshwater environment. And if I've read the article right, is talking about balancing nutrients in the Freshwater environment. In SW, the method is applied as the ratio required to reduce nutrients in the system. Same principles, but applied for opposite reasons.

The OPs problem pertains to hair algae in SW. Different algaes have different treatment methods (as mentioned about Bryopsis above)

I'm not disputing the info you've provided, in fact, I'd never thought about with Freshwater (I don't have blue/green algae problems), and if I do get some, I'll apply the theories - This is probably a good topic/discussion for the Freshwater Advanced forum, I'd never seen it referred to (Redfield) in Freshwater algae treatment, it's always been a topic for Saltwater Nutrient Reduction.
 

marine590622

Hi, yep, I understand the process (I use bio-pellets and was nitrate limited), but respectfully, your link refers to a freshwater environment. The OP is talking about a Saltwater environment - where there is minimal CO2 due to high water flows and surface agitation (CO2 doesn't last long in SW), and especially if running a skimmer injecting lots of oxygen into the water. Thus the carbon aspect of the ratio is important. For Redfield to work in SW, we need to add a carbon source (Vinegar/Vodka/Sugar or similar)



The link you provided also specifically talks about blue-green algaes in a freshwater environment. And if I've read the article right, is talking about balancing nutrients in the Freshwater environment. In SW, the method is applied as the ratio required to reduce nutrients in the system. Same principles, but applied for opposite reasons.

The OPs problem pertains to hair algae in SW. Different algaes have different treatment methods (as mentioned about Bryopsis above)

I'm not disputing the info you've provided, in fact, I'd never thought about with Freshwater (I don't have blue/green algae problems), and if I do get some, I'll apply the theories - This is probably a good topic/discussion for the Freshwater Advanced forum, I'd never seen it referred to (Redfield) in Freshwater algae treatment, it's always been a topic for Saltwater Nutrient Reduction.


Thank you for the clarification, I have yet to run out of freshwater fish that I want to keep so I have not stepped up to play with the salt water side of things. That said, I was concerned with the idea of using a blackout to treat for algae in a saltwater tank with corals as from my reading light is absolutely critical to maintaining healthy corals.

So on the salt water side of things you use the redfield ratio to intentionaly create algae of one sort or another so that by physical removal of the algae you can achive physical removal of the nutrients?
 

ryanr

Sorry to derail your thread DearPrudence (well sorta, it's still related to algae control)

So on the salt water side of things you use the redfield ratio to intentionaly create algae of one sort or another so that by physical removal of the algae you can achive physical removal of the nutrients?
Not exactly, the concept (carbon dosing which relies on Redfield) is used as a means of reducing nutrients (NO3O4). By removing said nutrients, most algaes cannot grow because there is no food. Unlike a planted Freshwater tank, where you still need the nutrients for the plants to grow, so a balance is required.
In SW, generally NO3 and PO4 are near undetectable. Most strive for 0ppm NO3, and <0.10ppm PO4, by having no nutrients, algae doesn't really grow (with a couple of exceptions such as Bryopsis and cyano)

I'll start a thread in Freshwater Advanced to continue the discussion. (probably tonight when I get home - and I'll move some of these posts to that thread )
 

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