From a mathematical perspective this makes sense as long as you have a tank where the nitrate produced from the fish waste is the same as the uptake of the plants. Seems like you would need to be very consistent in that plant mass to be able to make sure you are neither accumulating more nitrates than assumed from the fish waste or have decreasing nitrate levels over the week due to uptake. I dose the entire tank to 20 PPM because it's so lightly stocked that 20 PPM nitrates are depleted over the course of a week. You could look at it as a 40 ppm water change dose (since I'm usually changing around 50-60%) but the accumulation is functionally zero. At the end of the day I think the selling point of EI is that it's just an estimate. It seems futile to try and figure out precise amounts.

I'm only measuring nitrates though. I do wonder if I'm accidentally accumulating certain nutrients that I'm not testing for.

I get what you are saying. You do need to take into account the fish load and plant mass for each tank.

And your dosing is interesting. You are saying you dose the entire tank to 20 ppm NO3, and at the end of a week it measures zero? If so, that is really something. Most tanks create some NO3 regardless of fish stocking. I know in my tank many plants (not all) would suffer when the water column got so low.

There has been much discussion over the years about the "optimal" level of ferts for plant uptake. That is saying if plant uptake is 3 ppm per day, could you just dose 3 ppm per day and keep plants happy? Could the plants extract enough for their needs with so little in the water column? The general consensus is no. Or is there an optimal level for plant uptake? A level that allows for plants to fully uptake all they need. Many think so. For instance, in my tank, it seems my optimal level is about 30 ppm NO3. But again, that has to be taken in the context of my particular tank, with my particular plant mass and mix of plants.

Now I wasn't going to get into fish waste/plant uptake, but it looks like we are going there. In the end it's still just math.

Let's take your tank for example. Front loading 20 ppm NO3 with no fish waste and weekly uptake of 20 ppm NO3.

It would look something like this..................



Now lets say you had a moderately stocked tank producing 14 ppm NO3 per week. Here's what that would look like.



Notice the NO3 level on Day 7 of week 11. Went from about zero to 28 ppm.

Now let's say we have a heavily stocked tank that generates 28 ppm NO3 per week. Here's how that would look.



Note the NO3 level on Day 7 of week 11. NO3 is now at 56 ppm.

So rather than looking at it as trying to get to a precise amount, I look at it as many times folks don't understand or know the broad range of what is going on in their tank. IMO, it does help to understand your tank and in general what is going on, and could very well have a bearing on how much and when you dose.

And I get what you are saying about EI being an estimate. But to me it's really a very broad starting point, and blindly following EI is not optimal for many tanks.

For instance EI would have me dosing NO3/PO4/K at 22.5/3.9/22.5.

My dosing is 10/3.5/15.

And it would have me dosing micros at 2 ppm Fe. My actual dosing is 0.525 Fe.

Just saying I follow a lot of great tanks (yours included!), and very, very few are dosing stated EI levels. They are dosing what works best in their tank.

P.S. If anyone wants to mess around with my spreadsheet calculator that includes fish waste/plant uptake, the link is in my signature below. Anyone can download it and use it however they wish.

... and there is also the potential impact of other nutrients, à la Mulders chart influences. I think this has something to do with the fact that so many of us (including me) find that plants are happier with far more of certain nutrients than they consume. This implies that ratios are involved. If only we could find those chains of optimum ratios, even if wide tolerances appear.

I find it interesting that there are so many variations of those levels, that are far beyond consumption, found in reports by members.

Yeah that is a good point. And gets even deeper in the weeds.

When I raise dosing of X, does that mean that plants like more X, or that Y is more available?

Now you are really getting into headache territory there!

Too bad there isn't an algorithm for Mulder's chart. You know, you could enter in your dosing level for one element, and it would provide the optimum amount of everything else in perfect ratio.

But doesn't work that way. Each tank is a unique eco system, and takes some trial and error to dial in. And in the end, once it gets dialed in, do we really know why and exactly what is happening? Not really. But matters little.

And not to get lost in this discussion is that fert dosing is only one aspect of keeping a planted tank.

Light level, CO2 level, and maintenance are all equally important, and it's worth it to get each dialed in.

P.S.

Here is Mulder's Chart for those not familiar with it.

Yup, and going even deeper, I suspect that this plays an important role in the permutations:

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My guess is that no one will ever be able to piece all of this together in our lifetimes.

Did I also mention the other possible overlay of ionic balancing (which actually might assist most in determining ratios)?

Yes, that's why I have always said that this hobby is part science and part art. And almost forgot should add part good old fashioned elbow grease!

If you rely strictly on the science and what you "think" or "calculate" should happen, IMO likely not going to go well.

I've been moving for a few weeks and completely neglected the tank, if you could see it right now you might not be so generous in your assessment

I don't know if it was a matter of the soil absorbing a bunch of nitrates after a long period of lean dosing or if the tests are off. I've been meaning to make a reference solution to see the accuracy of my tests. It does seem suspicious that our experiences with uptake would be so different seeing as my tank is not THAT lightly stocked.

At least I understand what you mean by "dosing the changed water" and "50% WC equivalent" now! I appreciate your unique perspective on things.
@Deanna do you ever post pictures of your setup? I'd love to see what you have going on.

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Probably more accurately described as "Ramblings"!

Not at this time. My fear is that, seeing such beauty, it would cause too many members to give up on the hobby.

@Greggz can tell you the alternative excuse that I use.

I appreciate your journal here @Greggz . Everyone chimes in and I've learned a lot about dosing here.

@Deanna so you're saying you're doing everyone a service by not showing your tank? JK It's hard to keep up with updates in general here. Everyone has been so busy lately. I enjoy reading your posts as well. Very insightful and a lot science behind them.

How 'bout you start with a single plant and then a group of plants and eventually a FTS. This way members will have a chance to slowly adjust to such beauty.

Now that was LOL funny!

Bump: I am not sure.......which one!

That tank is a riddle wrapped in a mystery inside an enigma.

But it's all good, @Deanna you know I look forward to and appreciate your contributions.

I have some reading to do, thanks for your detailed dosing post. I was wondering, how did that Erio Vietnam do? Can't see it in the FTS, but I can't imagine it wouldn't like your tank better than mine!

Well the Erio did well, but I just didn't have room to keep it. As you might have noticed, I am out of real estate at the moment. And I have others right now that I am considering removing. Just can't seem to decide which ones.

I look at my tank like a puzzle. Trying to get all the parts to fit together to create something. At times I think I am getting somewhere, and then sometimes seems like a bunch of loose pieces just tossed anywhere. But I guess that is a good thing, keeps it interesting.

But the Erio did go to a good local home here. So as far as I know it lives on.

Might be my favorite plant right now.......Cabomba Furcata.