Duckweed Index questions

[Nont]

Hi everyone,

I’m currently use a complete fertiliser for my all of my aquarium, and I usually follow the dosage and frequency instructions on the bottle. I must admit that I have not a single idea of how chemistry works but I want to try out the duckweed index to reduce ferts expenses so I purchased some Limnobium to try out duckweed index. As far as I understand and if I’m not wrong, Duckweed index is basically means to add fertilizer to the tank when floater plants are sending out new leaves more slowly and showing signs of deficiency?

My question is as follows: If I were to use a complete fertiliser, how do I know how much to add? do I have to use the same dosage written on the bottle? And do I have to add fertiliser every time I do water changes or simply just look at the floating plants?

 

[LMuhlen]

While I haven't been able to implement the use of the duckweed index yet, my understanding is that it will be a trial and error approach, iterating and refining until you reach a new equilibrium where everything works out.

If you want to reduce ferts expenses, you would implement a new leaner fert schedule and wait for the floaters to react to it. Then you would evaluate if they liked it or not, and improve from there.

Then you can try not adding after every water change and see what happens...

It comes from a premise that every tank has different needs, so it allows you to test and learn how your own tank works.

 

[dw1305]

Hi all,

As far as I understand and if I’m not wrong, Duckweed index is basically means to add fertilizer to the tank when floater plants are sending out new leaves more slowly and showing signs of deficiency?

Pretty much, leaf size, as well as colour, is quite important - <"The scientific background to the "Leaf Colour Chart"">. Have a look at @Cédric's <"post and links">.

The reason I like a floating plant is that it takes CO2 and PAR out of the equation, and the reason I settled on Amazon Frogbit (Limnobium laevigatum) was

• It has a leaf green leaf (like <"Rice (Oryza sativa)">),
• isn't bothered by water hardness or alkalinity and
• shows a <"very plastic growth response to nutrients">, everything from <"triffid"> to <"running on petrol fumes">.

I'm actually using a <"hybrid Duckweed Index"> now, where I'm adding iron (FeEDTA) on a regular basis, partially because <"you get a lag phase"> before new growth appears, when you can't judge greeness (and nutrient status).

I haven't done it yet, but I will have a run out with adding in <"Phyllanthus fluitans as well">.

My question is as follows: If I were to use a complete fertiliser, how do I know how much to add? do I have to use the same dosage written on the bottle? And do I have to add fertiliser every time I do water changes or simply just look at the floating plants?

If it has the <"nutrient breakdown">? You can work out a level for one nutrient and then from that <"value work out all the other values">. Have a look at <"Low Tech Fertiliser Dosing. Whats your technique?">.

cheers Darrel

 

[Nont]

Sorry for the late replies but I’m thinking for some more questions…

The reason I like a floating plant is that it takes CO2 and PAR out of the equation, and the reason I settled on Amazon Frogbit (Limnobium laevigatum) was

• It has a leaf green leaf (like <"Rice (Oryza sativa)">),
• isn't bothered by water hardness or alkalinity and
• shows a <"very plastic growth response to nutrients">, everything from <"triffid"> to <"running on petrol fumes">.

That’s nice knowing that it can detect higher nutrients level as well. Do you know if the floating plants do generate more roots in lower nutrients? I realised that larger plants, such Cryptocoryne and Echinodorus, frequently almost die from root bound, growing more roots than foliage when I reduced the fertiliser dosage. But darker and larger leaves, small amount of roots in high nutrients environment.

I did have I've been reading and studying some chemistry lately, but I still don't see how to apply it to our hobby just yet, it is really confusing to understand the fertiliser discussion. And I know it's a dumb question, but are you the first to develop this method in aquarium? @dw1305

 

[dw1305]

Hi all,

Do you know if the floating plants do generate more roots in lower nutrients?............. But darker and larger leaves, small amount of roots in high nutrients environment.

I'd guess that they do, it is true for most plants, but I don't specifically know for Limnobium about root : shoot ratio.

I actually don't tend to worry too much about root development, <"leaf size and colour"> are my main metrics, mainly because a quick look (<"or photo">) is all that you need.

The "Duckweed Index" is honestly is the <"quickest and easiest test kit">. From <"Limnobium laevigatum - Tropica Aquarium Plants">.

Limnobium isn't actually <"widely used in phytoremediation">, purely because <"Pistia and Eichornia"> grow much more quickly <"https://www.sciencedirect.com/science/article/pii/S0301479718312040"> in high nutrients.

....... but are you the first to develop this method in aquarium?

Article One: @dw1305 invented the Duckweed Index.
Article Two: If he didn't, see Article One.

Yes and no. It was a <"cut and paste job"> in some ways, but I'm the person who has developed it to its present state, adding in the <"Leaf Color Chart"> etc. Personally I think the more people who try it the better, and over time they <"may refine and improve it">.

I don't derive any <"financial benefit from people using it">, but it does <"massage my ego">.

cheers Darrel

 

[_Maq_]

The UKAPS Constitution:
Article One: @dw1305 invented the Duckweed Index.
Article Two: If he didn't, see Article One.