Yellowing frogbit: need to dose more?

Jack B

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I'm already dosing TNC Complete at double the recommended dose, daily - but my Amazon Frogbit persists with having a few yellow leaves. Can it really need more ferts, should I turn my attention elsewhere, or is this just normal? 20200803_144853.jpg
 

dw1305

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Hi all,
but my Amazon Frogbit persists with having a few yellow leaves
That looks pretty healthy, just pinch off the old yellow leaves when you give it a thin.

Because it is producing new leaves the older leaves will begin to lose their access to the light and the plant will withdraw the chlorophyll etc from them.

cheers Darrel
 

Jack B

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London
Hi all, @Jack B , how is it looking now?

cheers Darrel
@dw1305 sorry for the silence - turns out being a teacher is hectic right now!

And thanks for asking: it's not too bad - though there is quite a bit of yellow around - pic attached. I'm minded to swap back from TNC Lite to TNC complete, even if my water board report puts nitrate at 40ppm... If you have more thoughts I'd be happy to receive them

Best wishes
Jack
20201114_181219.jpg
 
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They look a good size so maybe Nitrate isn't the issue. Are you adding any Magnesium? To be fair I would probably still go back to complete. The water report isn't cast in stone just an average of when they were testing. Over time with just partial water changes in a well planted tank it won't take long to burn off that nitrate.
 

Jack B

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They look a good size so maybe Nitrate isn't the issue. Are you adding any Magnesium? To be fair I would probably still go back to complete. The water report isn't cast in stone just an average of when they were testing. Over time with just partial water changes in a well planted tank it won't take long to burn off that nitrate.
Thanks! When I get some time I plan to read up on EI and do it properly. In the meantime, no I'm not dosing Mg - might I need that on top of TNC? I'm a chemistry teacher so should be able to get some on the cheap :) Is Epsom Salts the recommended form?
 
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Yes buddy epsom salts is the one. I've just had a quick look at the TNC stuff and there is the same amount of magnesium in both lite and complete albeit in small amounts. My understanding of using Duck weed to look for deficiency is new leaves would be iron, old leaves potassium and nitrate which the plants consume the most of. That just leaves magnesium which affects old leaves also. Potassium and Nitrate can also cause stunted growth in new and old leaves but yours look reasonably healthy. I would remove any poor foliage from under the leaves and have a shot with the magnesium, I think magnesium is mobile so you should see the leaves green back up if that's what you're lacking. @dw1305 is really the man for this one though, Duck weed index is his baby.

There is a law whose name escapes me right now, liebrig or something or other? It dictates that plants need all the trace elements plus N,P and K to form healthy plants if any of the above is missing it weakens the plant, look at it like building a wall without sand. That's why it is better to use a complete style fertiliser and ignore your water report. If there is some nitrate of phosphate coming out your tap then happy days you're belt and braces. Or you could save yourself a few quid and just buy the raw salts and mix it up yourself. Being a chemistry teacher you'll probably know better than most :)

Regarding EI, Basically all those elements we mentioned earlier are put into the tank in amounts that the plants couldn't realistically use even under maximum growth and lighting. It is really for the high tech people who don't want to run out of ferts while they are pushing growth to its limits so they can concentrate on getting flow and co2 injection right. Us low tech users just need to make sure there's some of everything. That's where the Duck weed comes in handy, it's close to the light and doesn't get co2 issues as it gets it co2 from the atmosphere and not the water column which we all know is in abundance in the atmosphere :( Duck weed reacts quicker to fert issues than the submerged plants so it's essentially a canary for the rest of the tank. 👍

Just to add, if it is nitogen you're lacking and there is a lot of nitrate in your tap water doing more or bigger water changes would help.
 
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dw1305

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Hi all,
@dw1305 sorry for the silence - turns out being a teacher is hectic right now!
I bet, my wife is a teacher, for the last couple of years she has been mainly working as a TA, but in 2020 a lot more time has been as a teacher and a lot less as a TA.
Yes buddy epsom salts is the one. I've just had a quick look at the TNC stuff and there is the same amount of magnesium in both lite and complete albeit in small amounts. My understanding of using Duck weed to look for deficiency is new leaves would be iron, old leaves potassium and nitrate which the plants consume the most of. That just leaves magnesium which effects old leaves also.
Try @AverageWhiteBloke 's suggestion, the plants look OK and a bit of extra Mg isn't going to do any harm. Your water won't contain much magnesium <"for geological reasons">, most of SE England has chalk aquifers, and chalk doesn't contribute much other than Ca++ and HCO3- ions.
I'm a chemistry teacher so should be able to get some on the cheap :) Is Epsom Salts the recommended form?
Yes, "Epsom salts" (MgSO4.7H2O) and ~10% Mg.
There is a law whose name escapes me right now, liebrig or something or other? It dictates that plants need all the trace elements plus N,P and K to form healthy plants if any of the above is missing it weakens the plant, look at it like building a wall without sand.
<"Liebig's law of the minimum">.

cheers Darrel
 
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