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Having gone over the 'daily dosing' thread which is currently being discussed on this section, got me to thinking about a few questions. Perhaps some folks will chime in with their opinions/knowledge here.

A lot of talk about N/P ratios. Am I correct in assuming there is no one 'perfect' ratio, but it is all dependent upon one's lighting, fish load tap water, etc? So in general, is it advisable to tell the 'typical' individual to tailor this ratio somewhere between 8:1 to 10:1 and play it by ear from then on, by observing their tanks? From what Error has found, he implies that 5:1 might be a better ratio.

How much do fish waste and food contribute to the nitrogen and phosphates in a tank? Is there a type of food which is higher than another in this aspect? What exactly is a 'heavy fish load' vs a low one or otherwise?

It seems to me, these are important factors in determing how one doses. In my case, I could never measure a drop in NO3 from water change to water change, though granted I never used the top line kits. I have, what I would consider, at least, a moderate fish load, and I do feed daily. So I am curious in getting some idea of how much this interaction of fish/food is having on my levels and plant's needs. I now dose N/P at water change (10/1.25) and midweek (5/.625). So far, not much of any noticeable changes, and thankfully, I am algae free. I will up the PO4 on one of the tanks to see if has any positive effect (as Error found).

Just some ramblings/ questions out there for others to comment on.
 

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Bert,

lets not confuse dosing ratio with water column ratio.
The thread about daily dosing is about dosing ratios and minimizing water changes.
You can be dosing NO3:pO4:K of 1.0:0.1:1.0 ppm every day for a week and have 20.0:0.0:10.0 in the water column on the end of the week. And 25.0:0.0:15.0 the week after, obviously not good. But if you test every week or two and keep getting 5.0:0.1:5.0 all the time, then your daily dosing ratio and quantity is good.
We are looking for the best dosing ratio that will keep desired water column levels constant for a long time without water changes.

Edward
 

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Bert,

If your algae free for a long time you mest be doing something right. By long tim e I mean a month or more. That is long enough for amn imbalance to lead to algae.

From what Error has found, he implies that 5:1 might be a better ratio.
Actually I think he has increased his dosings ratios to get closer to 10:1. Much of what we were discussing was about finding the "balance", not necessarily what the plants get or need.

I am not sure of the extent that fish loads and feed play in this. That is something I was wondering and I'm glad you asked. I tend to feed very lightly but I am starting top feed more. I know that the amounts of naturally occuring N and P are probably more than we give credit for. One thing I have heard asked, but never really saw and answer for, was how much of the N produced by fisha nd food actually makes it to NO3 and how much is taken up by the plants as NH3/NH4? What difference does the N source make to the plants? In a cycled tank you will not see NH3/4 or NO2 due to the bacterial load, I wonder if the plantes ever actually get a shot at anything but NO3.

Your dosing ratio is 8 (N/P) which is recommended with a low fish load, lightly feed tank. A ratio of 10 is more suited to a higher fed tank were more N/P comes from the bioload. You are dosing 15/1.875 N/P . I have been dosing 16/2 in my lightly fed tank and am now uping that to 20/2.3 due to some plant health issues I attribute to low N.
 

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Bert,

I never test my water, so I never know exactly how much of what is in there. I just keep an eye on the plants and dose according to a few assumptions.

Excessively high light tanks (which to me are a completely different animal) need more, and not just because it's all taken up by the plants, but because some of what you add is reduced by light (Fe/P comes to mind). I think that's what was happpening to my P before I doubled the dose (5.5wpg).

I don't know what the N/P ratio in my water column is, and frankly it makes no difference. I'm just trying to find a good threshold with this tank and I will treat whatever symptoms as they come until then.

Dennis,

I would guess that most, if not all N from fish food is ammonia right off the bat. From there the unused is perhaps converted on down the line. I don't know enough about the nitrogen cycle in aquatic environments to say this with much conviction, however.
 
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