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This is actually my barebottom. I have fuge with cheato and tukani live rock. The cheato won't pull out all the phosphate because there's no nitrates...
So if I understand you correctly, you have a high phosphate issue that you are unable to resolve while relying on macro algae to consume it, and that is because your nitrates are too low?
Are you combating PO4 buildup (something else?), or simply trying to maintain some arbitrary nitrate level? Just curious!
-Matt
What are you using for kno3?
redfield ratio is not for maintaining an arbitrary level. based on that ratio, both PO4 and NO3 move in sync at that given ratio. I forgot what that exact number is but it's easily searched. Since the lower number is NO3, if you are nitrate limited, your PO4 won't go down anymore. So the theory is to increase NO3 so that the PO4 can drop (together w/ the NO3). Once you bet back to 0, you can add more NO3 and continue to cycle.[...]
However, looking at the composition of individual species of phytoplankton grown under nitrogen or phosphorus limitation shows that this nitrogen to phosphorus ratio can vary anywhere from 6:1 to 60:1.
Although the Redfield ratio is remarkably stable in the deep ocean, phytoplankton may have large variations in the C:N composition, and their life strategy play a role in the C:N ratio, which has made some researchers speculate that the Redfield ratio perhaps is a general average rather than specific requirement for phytoplankton growth
That's what I was thinking you were using. I'm leaning towards using potassium nitrate because instant ocean needs a little bit of potassium dosing anyways. I'm dosing kalk in this tank, so calcium nitrate would mess my CA/alk balance all up.
I agree in part, but I don't know that's what the Redfield ratio indicates (nutrient levels "moving with each other"). I do see people using it that way in reefing occasionally.
I think Redfield can be used as a guideline to know when a system is out of balance, but I'm not sure it's an absolute measure even then. I believe you need a baseline to compare with for a given ecosystem to be able to form judgements about "good" or "bad" levels.
not that much. It takes very little calcium nitrate to maintain 5ppm or so nitrate.
I agree w/ you but I think in this case and my own, it's the conclusion (anecdotal) that in order to lower PO4, we need to increase NO3. The baseline fact of high PO4 is already established, the redfield ratio is just used as a guideline to a technique to lower nutrients but not as a way to lower nutrients. Hope I'm making myself clear.[...]
The most common I have read about is sodium nitrate. If I had to guess without looking its because sodium is probably one of the more abundant elements in salt water thus making a small change insignificant. Second would the the CaNo3 because calcium is also very abundant. Potassium on the other hand is used less by corals and probably the least abundant of the 3.
We can debate for years but randy Holmes Farley can tell you a definite answer in about 2 paragraphs. Before you dose anything I would ask his opinion.
[...]randy Holmes Farley can tell you a definite answer in about 2 paragraphs. Before you dose anything I would ask his opinion.
The problem with using sodium nitrate would be the rise of salinity. We use calcium chloride for increasing or calcium. When the sodium and chloride combine it will make salt.
The problem with using sodium nitrate would be the rise of salinity. We use calcium chloride for increasing or calcium. When the sodium and chloride combine it will make salt.