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WillsC

Azolla issues

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I'm not 100% sure this is the right forum for this and if not Mods please feel free to move it.

 

I have 28 300 gallon totes plumbed together.  14 have tilapia in them and the other 14 have duckweed and azolla, no fish.  On the plant side of the greenhouse the pumped water comes back to those tanks a couple inches below the surface so no splashing.  The azolla has grown amazingly well could not be happier with it except for some reason that baffles me a tank of it will start to show a little brown and within a couple of days the entire tank of azolla is dead and gone but the duckweed mixed in remains alive and happy?  The tank next to it meanwhile is full of azolla and perfectly happy?  All the water is the same, it is all one system.  Any ideas why this happens and has anyone else experienced the same?   There are some tadpoles in the tanks but I would assume they are in all the tanks without fish.  They are tree frog tadpoles if that matters.  

 

 

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I've had that issue myself over the years, but mainly during the summer.  Best I was able to figure was that azolla gets too hot and then dies.   Check the water temperature in the azolla tanks and see if there is a difference.

 

My experience azolla grows best in the winter and duckweed best in the summer.  Oddly enough if I shaded the azolla in the summer it did better.

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Ravnis,

 

That was my first thought also but the tanks are side by side one thriving one dead.....same temperature as they are all plumbed together.  I can't figure it out.  

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Might try rigging some shade over the tank that's dying out.

 

I was growing azolla in kidde pools the 8ft diameter ones ~2ft deep and some would grow well and others not at all.  They all had the same waste nutrient from my solids filter and fish tank water.  The only difference was due to the treeline on my property shading some tanks more than others.   Seems the ones that got early morning sun , but shaded by the afternoon did best.

 

I also added iron and magnesium as that tended to show as a deficiency for me with my other plants. 

 

By the way just because the system is plumbed and circulated together does not mean zones of varying water temperature can't form.  I found as much as a 6 degree change from one  area to another in some of my early systems.  This might not be the case with your system , but if you check in various places in your tanks you can verify if there might be a circulation issue that was not immediately obvious or at least rule it out.

 

These are just some ideas off the top of my head.   Hope it turns around for you.

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I have experienced this issue several times..At one event we identified that they need more phosphates than other plants in Aquaponic systems and also came to know that they could absorb atmospheric ammonia..One agricultural scientist suggested to try a product called Azo-Phos and the issue was resolved then. Later we began to design decoupled azolla systems where we add organic manure such as dried cow dung powdered along with some compost or compost tea or some good healthy soil. It is working.

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Ravins,

 

I will check the temps, maybe you are right and there is a variation in temperature among the tanks.  Just a degree or two could cross the tipping point.  

 

Vkn,

 

I'm pretty sure it is not phosphate as I am on a lime rock well and they mine (or use to) phosphate here in central Florida.   

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