Weekly nutrient consumption in planted aquarium

[Tim Harrison]

Ardjuna, please don't misunderstand me...I'm not seeking scientific rigor...I'm simply pointing out that your study, nice though it is, simply lacks it - and for what it's worth you may as well save yourself the bother of all the hard work because your study will yield comparable results to those achieved using the EI methodology explained above... however with the following major differences...fine tuning EI is simple, and easy.

 

[Marcel G]

Yes, I understand that, but as I already explained, my goal is different, and your suggested way of fine tuning EI may not lead me to this goal any closer.
I have an experience with my high-tech tank, that when I practice very lean fertilizer dosing, my plants are doing just fine, but the growth rate is much slower. According to my observations the growth rate has much to do with phosphates level. Whether I have 30 mg/L NO3 or just 5 mg/L NO3, the plants grow +- the same if the PO4 level is the same. But when I add more PO4, the plants begin to grow like mad. So it seems that in high-light (CO2) tanks PO4 is probably the bottle-neck. I would like to find out what nutrient levels are needed for good slow growth in average planted tank. Your suggested way of fine tuning EI can be also one way of getting some raw idea, but as with other suggested methods, I'm afraid that it doesn't count with substrate, filter media, bacteria etc. So on one hand I can find out what minimum level is still bearable for my plants, but on the other hand I'll have no idea of how much nutrients ended up in the substrate or filter. Beside this, there can be some shortage of just one or few nutrients which will cause my plants to show some deficiencies, but still other nutrients could be in rich surplus without me having any chance to know that. The main problem with EI is that the nutrient ratio is 30 : 3 : 20 : 0.5 (N : P : K : Fe), but are you sure this ratio is correct? I mean, if you lower the EI dosage (e.g. to 2 mg/L NO3, 0.2 mg/L PO4, 1 mg/L K and 0.03 mg/L Fe per week), and the plants begin to show deficiencies, how you know which nutrient became the limiting factor (bottle-neck)?

Another problem I see with EI metod is that the proponents of this method say very often, that when you get algae, it means the plants are not growing well. This is according to me a complete nonsense. It seems like no one of them is able to admit, that the algae can be related to much more factors then plants alone. Also as already pointed out in some earlier posts, the algae can be suppressed by higher amount of nutrients, so not plants but higher levels of nutrients can be the primary cause of algae suppression in many tanks. I want to say by all this, that when I lower nutrient levels, and get some algae, it may not mean that my plants are not growing well. I may mean that the algae are no more limited by the higher levels of nutrients.

 

[Tim Harrison]

Your suggested way of fine tuning EI can be also one way of getting some raw idea, but as with other suggested methods, I'm afraid that it doesn't count with substrate, filter media, bacteria etc. So on one hand I can find out what minimum level is still bearable for my plants, but on the other hand I'll have no idea of how much nutrients ended up in the substrate or filter.

Exactly, I couldn't disagree with you less - those are just some confounding factors - that is why either way the results will be equally meaningful/meaningless, so you may as well keep it as simple as possible and use the EI methodology.

Beside this, there can be some shortage of just one or few nutrients which will cause my plants to show some deficiencies, but still other nutrients could be in rich surplus without me having any chance to know that. The main problem with EI is that the nutrient ratio is 30 : 3 : 20 : 0.5 (N : P : K : Fe), but are you sure this ratio is correct? I mean, if you lower the EI dosage (e.g. to 2 mg/L NO3, 0.2 mg/L PO4, 1 mg/L K and 0.03 mg/L Fe per week), and the plants begin to show deficiencies, how you know which nutrient became the limiting factor (bottle-neck)?

The EI ratio of nutrients was just meant to be a rough guide...if you play around with the ratios a nutrient at a time you will still reach your goal but perhaps with less work.

Another problem I see with EI metod is that the proponents of this method say very often, that when you get algae, it means the plants are not growing well. This is according to me a complete nonsense. It seems like no one of them is able to admit, that the algae can be related to much more factors then plants alone. Also as already pointed out in some earlier posts, the algae can be suppressed by higher amount of nutrients, so not plants but higher levels of nutrients can be the primary cause of algae suppression in many tanks. I want to say by all this, that when I lower nutrient levels, and get some algae, it may not mean that my plants are not growing well. I may mean that the algae are no more limited by the higher levels of nutrients.

I think it's perhaps widely accepted that the presence of algae is due to various factors often interacting synergistically, too much light, high levels of organics, poor plant health etc - and that's not mentioning confounding factors. Accordingly, it would be nigh on impossible to determine with any degree of significance the exact role played by nutrients in any one particular circumstance. Suffice to say EI recognizes this and accounts for it pragmatically in a simple and effective way. But playing around with EI ratios may still give you some idea of what works to help suppress algae within your unique tank conditions...but either way, exactly why will still remain debatable...

 

[Marcel G]

Thanks Troi for your comments. I have to think of it.

 

[Tim Harrison]

At the end of the day it's still an enormous amount of work for very little gain...which is why Estimative Index was conceived in the first place and why it remains so popular. It means we can effectively rule out nutrient deficiency and get on with the more difficult problems of optimizing light, CO2, flow, and distribution.

 

[Andy Thurston]

Isn't darrels duckweed index at the opposite end of the scale. i know is not intended for hightech tanks but surely it could be modified so you can keep nutrients to a minimum in a hightech.

 

[Michael W]

Isn't darrels duckweed index at the opposite end of the scale. i know is not intended for hightech tanks but surely it could be modified so you can keep nutrients to a minimum in a hightech.

This is a possibility. If CO2 flucuation is to blame for the average algae caused in high tech tanks then floating plants could help to test if that is the case, since they have unlimited access to CO2. If the floaters look stressed then one factor could be nutrients and not CO2. This will allow us to get some ideas on what nutrients are lacking over CO2 by dosing different nutrients and see which has the most impact on new growth etc. Granted there are limitations as apparently some floaters won't like the flow provided in high tech tanks or they may suffer from lens burning. But this could well work.

But Troi has my backing on this subject, I don't tend to like to fuss over statistics. I hate over thinking so much. I do not mind reading up on this subject but in practical terms I won't stress over details if needs be.

 

[Andy Thurston]

Maybe you could use emergent growth instead of floaters as your indicators.
I'm not overly fussed for the numbers either but the idea of keeping more sensitive shrimp/fish in a hightech interests me. I've been talking to a shrimp supplier and i believe its possible with lean dosing and this could be the missing part of the puzzle.
If you play the numbers game then i think you will encounter many problems but if you have a few species of indicator plants i think it would be much easier to manage
Just my thoughts

 

[dw1305]

Hi all,
This is an interesting thread.

As "Big Clown" suggests the "Duckweed Index" is just a simple way of ensuring some plant growth. At least one nutrient will always be limiting plant growth, and usually this will be nitrogen (N), but it could be any of the other macro or micro-nutrients with potassium (K) the next most likely followed by phosphorus (P) etc.

Ideally I would have liked to quantify the nutrient levels, but it is problematic, particularly for anions like NO3- and PO4---.

Maybe you could use emergent growth instead of floaters as your indicators.I

You could, it just has to be a plant with access to both atmospheric CO2 and a reasonable amount of light.

I like the "Duckweed Index" because it is a simple, flexible methodology and you don't need to measure anything. If the floating/emergent plants are green and growing, don't do anything, if growth or colour declines add NO3- and K+, if the plants don't show a very quick response, it means neither N or K weren't the limiting nutrient, and you can add some Mg++.

Nitrogen, potassium and magnesium are all mobile within the plant,so you get a rapid response to increased availability. Because non-mobile nutrients would take longer to show a response, rather than going through adding one new nutrient at a time, I just add a complete fertiliser at this point.

If you wanted to you could straight to the complete fertiliser stage, it really is that easy.

cheers Darrel