Comment

Comment by Jake Schneider on August 19, 2011 at 10:10pm

What we need is a fish/plant friendly dissolvable fly paper.  Just set it under the porch lights and throw it in the fishtank in the morning.  Any chemical engineers in the house?

Comment by BullwinkleII on August 7, 2011 at 6:16pm

Thanks everyone, I'll shoot for 25c or so with the duckweed tank.

 

Comment by Kobus Jooste on August 7, 2011 at 12:01pm

As mentioned, the first sign of distress was around the inflows

By the end of the day it looked like this.

 

I have seen dead or unhappy duckweed before, but nothing like this.  Kind of like you poured bleach in on the one end and just watched them die off rapidly.  I have never seen it again although right now I battle with little patches of fungi every now and then.  Must be something that got into the system and manages to survive the UV sterilizer.

Comment by Kobus Jooste on August 7, 2011 at 11:54am

Bullwinkle - I have Lemna gibba (fat duckweed) that I have pushed to 33 degrees Celcius (water temp) before, but I crashed that population momentusly.  I think it was a fungal infection (spreads on the surface of a dense colony) that spread like wildfire, as the whole set-up was dead in a day. Most references that I have found puts lower 30's as the upper limit.  At those temperatures, I think they are a bit vulnerable though, especially to stuff that may not show up at lower temps.  Right now my system is in winter mode but is still yielding very well - around 1.5 kg wet mass per week from 7 square meters of bed on a nutrient loading of under 20 grams of fish food per day.  The upper cm or so of water in which they sit actually gets far hotter as the colony prevents circulation.  I'm installing extractor fans before it gets too hot this year (all the vents were open and I still got 33).  I also installed 40% shade netting inside the system, which is a polycarbonate structure of 27 m2)  

Comment by TCLynx on August 7, 2011 at 11:10am

Bullwinklell, I believe Kobus has encountered killing off his duckweed variety with high temperatures before.  I believe it is the water temp that kills it not the air temp.  I've had some local variety here that was surviving fine in rather warm water as long as it was in very heavy shade.  I have another sample that I put into a different pool as was doing well even in +30 c water until I gave it a dose of ammonia and now most of it has turned white so it seems like a combination of factors will be involved.

Comment by Carey Ma on August 7, 2011 at 10:11am

It is so unfortunate that the US gov led the way and chose to eradicate our freedom to grow and soiled the name of hemp. Farmers here can grow up to eight plants for fiber, feed and seed. No unfortunately I do not count and am therefore disqualified. Sigh. Hemp is THE most versatile plant on this planet. Truly a miracle plant.

Oh hey, a shout out to the peace puffers. ;)

Comment by RupertofOZ on August 7, 2011 at 9:04am

Yeah most definitely Bullwinkle... you'll kill the duckweed off with temps over 30c for more than a day or two... indeed 28c is probably about the limit...

 

You can get a "giant" duckweed variety that handles higher temps though.... which is the "major" version of the plant genus... and prolific in the Northern Territory..

 

Comment by BullwinkleII on August 7, 2011 at 8:36am

I've just set up a hothouse, and collect some heat from 4mm poly strung up near the top, and pump it down to a duckweed tank near the FT at the bottom in an attempt to "buffer" my FT temperatures. I'm seeing temperatures around 36c in the water entering the duckweed tank.

 

Does anyone know the maximum temp duckweed can handle, and or it's prefered range?

Or even if you don't know, does anyone have any experience of wiping out their duckweed where they thought it was a temperature based issue.

Comment by Carey Ma on August 7, 2011 at 7:26am

All smiles...thanks, you are a true sweetheart.

Comment by TCLynx on August 7, 2011 at 7:23am

I know you posted it some where Carey because I remember reading it.  I'm going to copy this comment and paste it into the Duckweed thread for you though since it is about Duckweed.

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