Lowering P and Fe increases NO3

[m2434]

Just a crazy thought.

If your primary method of nitrate export is say algae. Wouldn't it be possible to have high N03 levels due to limited PO4 and Fe? With the prevalence of GFO, RO/DI and other phosphate reduction methods, how common could this be?

Granted feeding will introduce phosphates, but low levels could still be a limiting (I think). And could decreasing feeding, or feeding low phosphate food, in theory increase NO3 under certain circumstances?

[bertoni]

Yes, that situation has been reported. I don't know of enough quantification on the subject to say much, but in some cases, phosphorus might be limiting, and dosing could in theory help. The same has been said about low nitrate limiting algal export of phosphate.

On the other hand, the source of most phosphorus and nitrogen in the water column is going to be food added to the tank, in the common cases. So decreasing the feeding would be unlikely to increase nitrate. One exception might occur when the food was high enough in phosphorus to add extra phosphate, and thus help remove a one-time nitrate addition. Changing to a lower-phosphate food might in theory allow more nitrate to build up in the water column.

Unfortunately, the ratio of nitrogen to phosphorus consumed seems to vary a bit, and there are other processes in our tanks (like skimming) that might throw a lot of wrenches into the works.

Dosing iron is generally safe enough that adding extra is unlikely to do any harm, so that's unlikely to present the same kind of difficulty as nitrate and phosphorus problems.

You could try reading up on the Redfield ratio, if you want some more details. It describes the ratio of nutrients in phytoplankton.

[m2434]

Great info, thanks bertoni!

[Mike O'Brien]

You won't be limited by Iron when using GFO.

[acrylic_300]

106 C: 16 N: 1 P: .001 Fe is the Redfield Ratio.


http://en.wikipedia.org/wiki/Iron_fertilization

They are thinking of dosing the Ocean with Iron to solve Global Warming.

[m2434]

Originally posted by Mike O'Brien
You won't be limited by Iron when using GFO.

Maybe, but what if you were iron limited? I guess a don't understand the nutrient dynamics of iron as well either and I'm not even sure if it's possible to get iron low enough to really have an impact.

Originally posted by acrylic_300
106 C: 16 N: 1 P: .001 Fe is the Redfield Ratio.


http://en.wikipedia.org/wiki/Iron_fertilization

They are thinking of dosing the Ocean with Iron to solve Global Warming.

I don't know, can increasing the oceans bio-load really help, or is that like sweeping dirt under the sofa – out of sight out of mind... for now.

[billsreef]

This has been discussed quite a bit in the plant forum. The most often observed problem is Nitrate limitation leading to elevated phosphate, the fix being add Nitrate as either potassium nitrate or calcium nitrate. Keep in mind that the only real problem with nitrates is as algae fuel, while phosphate is both algae fuel and limits calcification or our corals. With rapidly growing fuge algae it is possible to maintain acceptably low nitrates (0 is not a necessary to shoot for) via additions and thereby maintain undetectable phosphates

[m2434]

I'm aware of nitrate dosing, but I was more curious about the plausibility of going the other way, with phosphate and/or iron limitation. How difficult is it to really maintain phosphates at a limiting level, say .03... and if you did could nitrate levels skyrocket? I guess if we use the Redfield Ratio, it would appear that very low levels of Fe, would be required for nutrient limitation; say, something like .00003. So, this might be unrealistic.

[billsreef]

Better off just paying attention to the N and P part of the redfield ratio and just ensuring that there is sufficient iron in any event. Notice that algae typically takes up 16 N for every 1 P. It's not unusual for people to have tanks running with undectable nitrates and yet having phosphate problems at the same time. How often do you see it the other way around without heavy use of phosphate removers? Since phosphate is a problem to our corals in minute quantities, and nitrate is not a problem for our corals in low levels it just makes more sense to maintain low nitrate levels and let the redfield ratio work for limiting phosphate

[m2434]

Originally posted by billsreef
Better off just paying attention to the N and P part of the redfield ratio and just ensuring that there is sufficient iron in any event. Notice that algae typically takes up 16 N for every 1 P. It's not unusual for people to have tanks running with undectable nitrates and yet having phosphate problems at the same time. How often do you see it the other way around without heavy use of phosphate removers? Since phosphate is a problem to our corals in minute quantities, and nitrate is not a problem for our corals in low levels it just makes more sense to maintain low nitrate levels and let the redfield ratio work for limiting phosphate

I would agree. However, you are assumeing there was at least a slight hint of practicallity in my thought proccess... I assure you there was none My intrest is more the theoretical implications