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View Full Version : Have you seen the automatic duckweed feeder?



Shas
12-10-2011, 02:50 AM
I think I'd place this downstream from my bell syphon
rather than running my pump intermittently,
but it's an ingenious concept:

http://tinyurl.com/7nyl27j

There is a side view link to the right of the animation.

keith_r
12-11-2011, 07:16 AM
bullwinkle (the author of that blog) does lots of experiments and documents them very well.. i enjoy reading his stuff, even if some of it confuses me

foodchain
12-12-2011, 06:32 AM
Duckweed does grow fast, but fast enough for daily dosing? That's going to be a huge resevoir of duckweed, and a small amount be dosed to allow it to reproduce fast enough to keep from losing the parent stock.

Shas
12-12-2011, 09:48 AM
I've never raised duckweed seriously
but according to the literature
it is capable, under ideal conditions,
of doubling its mass every 16 to 24 hours.
Perhaps Bullwinkle is providing optimal conditions!

keith_r
12-12-2011, 11:32 AM
it really doesn't take a lot to get duckweed really growing.. heck, i have it growing in my basement with a fourescent light 4' away from it, and the water's gotta be about 64f..doesn't even need much aeration (i had 0 air going into a little pond last summer and ended up composting quite a bit of it)

120ThingsIn20Years
12-15-2011, 10:04 PM
Hi people, Bullwinkle here.

I noticed my duckweed feeder idea was here and thought I'd drop in and get some feedback and clear a few things up.

Firstly I haven't actually made it so I cant be sure that it does work, but I have done a LOT of tests. I unfortunately had to move away from the farm I lived on with a stack of space for my 2 IBC and 3000L grow bed system, and the 2 1.5 square metre duckweed tanks :(

My current system doesn't allow anything like the size of duckweed feeder I had planned. It was originally to be two rubber lined halves of a square 1000L rainwater tank, cut for maximum surface area. Now my duckweed is growing in a 60L tub.

So originally I had planned something like 3 metres square of surface area for duckweed growth, but even on a smaller scale, the system should work.

I've done a lot of experiments with the way the stuff moves when you add water, and from what I've seen, it should work just as well if the outlet nozzle (ie the standpipe that carries the feed to the fish tank) was built into a gutter made from 30mm PVC conduit, with a 12mm hose for the standpipe. The Dose with such a design would be more narrow (due to being only 3mm wide) and the length is set by how far the water entry point is away from the end of the conduit, and how far the stand pipe is set from the end of the conduit.

The result is, on the small scale tests I did, I can deliver literally 20-30 leaves at a time if that's all I want, or a cup full or more each time the flow is on.

Oh, and good idea about using the flow from the siphon. I hadn't thought of that. I currently run a single blue barrel, half GB, half FT, so that would suit my system. Thanks for the tip :)

The layout I'll build for this system would be a length of 30mm conduit sliced in half lengthways to create a gutter going from my duckweed tub, to a small diversion of water from the outlet of my bell siphon. Given the growth rate I see in my duckweed (in a small glass house so I would say it's pretty close to duckweed heaven) I can feed the fish around a heaped teaspoon twice a day.

If you take an amount of duckweed out of a tank, the remaining weed spreads out right away to take up all the space, so it just gets thinner and thinner. The result is if it gets a little low, the device would be feeding less with each dose as it only feeds a given surface area of the conduit.(in my case perhaps only the last 2 cm of the conduit) This means you can never really run out because the less there is the less is delivered.

I had never planned on being able to feed my fish on duckweed, but I just feel it has to be a good thing to give them some variety. I also like duckweed, because it just floats around and wont rot if you over do it. It also inst quite as popular as my fish feed, so the runts get to feed on it at their leisure, so don't get bullied out of all their feed.

As for my blog, if there is anything that wasn't understood, I'd love the feedback on it, as I'd rather it was useful and clear.

I try to tread a fine line between being informative, inventive, and being entertaining and find all three a challenge most of the time :) But it is nice to stumble upon people who have read it. There are plenty of numbers, and stats, but sometimes I wonder if it's just my dear old mum hitting reload thousands of times :)

So let me know if there is anything that's not clear enough and I'll fix it, but keep in mind sometimes the reason the info isn't there is because I simply have no idea what I'm talking about :)

Well that was an odd post for a new comer to your community, so I'll still be here, but I'll have my head down reading threads for the next few days like a newbie should.

What I've seen so far looks interesting.

- BullwinkleII

NeverResting
12-01-2012, 03:39 PM
Great little idea there. I got some duckweed recently with a batch of fish (not tilapia) and am waiting for it to start spreading out some more.