Comment

Comment by Carey Ma on August 6, 2011 at 8:11pm

(I thought I posted this before)

Here's my two cents:

I use to collect as much (wild) duckweed as I wanted from the many irrigation ditches/ canals around the village but was a little concerned about any pollutants that might end up in me so I started to grow my own

I grew duckweed in several large long beds (4' x 16' x 5") that flowed directly from the fish tank's and duck pond's solid waste filter. An air pump was attached to the outside connected to three circular air stones and placed in the bottom. A plastic platform with legs and holes drilled into it used to separate the perlite and crushed bricks (like in a wick systems). The filter consisted of air-stones, separator, perlite and crushed bricks with a layer of geotextile in between each layer except for the separator. There I used a mosquito screen. Another piece of geotextile was placed on top followed by a piece of river rock where the water splash. Worms were placed on top of the geotextile to eat up and break down all that fantastic poop.

 

From the duckweed grow-beds, water was siphoned off the bottom of the beds into a connection at the bottom of a bucket. A brick or two was placed in the bucket to deter any plants that might accidentally get in from going across the bucket and directly into the exit hole on the opposite side (idea taken from septic tanks). I simply scoped (netted) any little wanderers off (if any) and added it to the rest of the harvest.

The collected duck weed is enclosed in an old T-shirt with the holes sewed shut and Velcroed, then squeezed and spun dry, after which it is placed in the solar dryer or freezer depending on what I was doing at the time. Either way the dried material was then ground into powder to add to the other ingredients, to make feed.

 

Duck/ Fish pond > solid filter > Duckweed beds > bio reactor > grow beds 1-6 > cistern + oxygen > fish pond > duck pond

Comment by Jay Wolf on April 8, 2011 at 10:18am

Thanks for the invite again TC!!!  I have heavy experience rearing fish but very little producing feed.  I have a grasp of what different fish need for nutrients to grow healthy and fast.  I hope I can help anyone that has questions.  Jesse Hull knows my mentor Fred Binkowski.  Fred has essentially taught me everything I know.

Comment by George T on March 31, 2011 at 6:19pm

Rick

Which mill are you using or do you intend to use?  Thanks

Comment by Rick Stillwagon on March 26, 2011 at 8:45am

I have mentioned how I am developing my system, part of it is using a pellet mill.  This is only for a convenient way to process and store the materials.  

Comment by Jesse Hull on March 28, 2011 at 12:12pm

RE: Does anyone know anything about preserving duckweed. Freezing or drying? Any info on how much nutritional value might be retained?

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Flash freezing is probably the best way to retain all the value; however, that's not a process commonly available to everyone. 

I would also think that drying it (removing the water) might be useful in achieving a uniform weight; however, it would need to be done so that the nutrients didn't get lost.  A measured amount of water could be added later, whether by mixing with other dry food ingredients or not, to obtain a determined specific gravity prior to creating flakes, pellets, cakes, etc.

This may sound like too much work, but the problem I see with what many speak of, e.g., tossing in duckweed by the handful, or just letting soldier fly larvae drop from the "pod" hung over their fish tank, is that you'll never be certain how much food is delivered to the fish (your crop, essentially). 

To be successful, whether it be to simply supply yourself/family with food or achieve a profitable commercial harvest, it is crucial to periodically sample and measure your fish to ascertain the correct feeding rates.  This is a lot of trouble to go through if we only relied on random or unmeasured feedings.  If, on the other hand, you feed a regular diet and consider the larvae or duckweed as 'extra', it could lead to over-feeding and water chemistry issues.

Comment by BullwinkleII on March 27, 2011 at 7:53pm

Does anyone know anything about preserving duckweed. Freezing or drying? Any info on how much nutritional value might be retained?

 

Comment by TCLynx on March 27, 2011 at 6:28pm

You hit the nail on the head there Jesse, Aquaponics is only closed loop if all the people eating the veggies and fish from the system are also providing all their waste to go back into the system, till then, we gotta feed the fish.

Comment by Jesse Hull on March 27, 2011 at 6:05pm

We use a standard recipe from Zeiglers at Sweet Water.  There has been talk of switching to another option; however, it hasn't gone beyond the discussion phase.

On a commercial scale, a lot of compost is produced.  I realize that this is probably nothing new to most folks here, but the vegetative components of this could be used to produce worms, providing an ancillary food source. 

A lot of fish carcasses & remains are also produced in a large scale facility, and just like the harvested effluent from RAS systems, this must be dealt with responsibly. Toward this end, I am personally very eager to try producing black soldier fly larvae.

Duckweed is a great protein source for Tilapia and other omnivorous fish; however, it does nothing in it's raw state for carnivores such as Perch.  I'm a big fan of getting nutrients from as many sources as possible, and duckweed grows really fast (I've seen populations double in just a few days).  So if it were cultivated to be combined and processed with other "carnivorous delights" into a feed, it might still be useful.

I'm on the fence about "the perpetual machine" argument.  Our planet is just such a thing, recycling the same cosmic elements for millions of years that have been around for billions of years.  Aquaponics attempts to bio-mimic by incorporating several components, but I have doubts as to whether it brings in a wide enough spectrum to qualify as a closed loop.  Especially on a commercial scale, it will remain necessary to calculate continuous inputs into the business equation.  I'm content enough (for now) in exploring ways of decreasing the level of those inputs, especially regarding the currently unsustainable sources of fish meal.

 

Comment by BullwinkleII on March 27, 2011 at 4:16pm

If I ever counted the hours I've spent arguing with people about why their perpetual motion machine doesnt work I'd go nuts :). 

 

I actually grow my duckweed in a tank with only a small aquarium air pump, and some pellets of goat dung added whenever the duckweed looks like it needs it. I figure saving my systems nutrient for my veggies is always a better idea.

 

This is just out of interest.

 

Comment by Walter Bernie Kerr on March 27, 2011 at 10:35am

I've been doing catfish cause I don't have to worry about temperatures for them either.  Bluegill are good eating. say TCLynx

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Hey, some of us think cats or as good as bluegills (bream to us ol' southern boys)

Comment by TCLynx on March 27, 2011 at 8:25am

My continued battle against the idea of the perpetual motion machine aquaponics is when people expect that they can harvest commercial quantities of food from an aquaponics system without needing to feed the fish anything from outside the system.  The Nitrogen, Phosphorus, Potassium and all the micro and trace elements being removed need to be replaced some how.  Now legumes that have a relationship with the nitrogen fixing bacteria going in a system might bring in some nitrogen from the atmosphere but I still don't see that as being able to provide enough to have a commercial harvest without feeding the fish more than the scraps of lettuce leaves.

 

Tod, I've not yet raised Bluegill in aquaponics but I know of people who have and I'll probably try some this year.  I've been doing catfish cause I don't have to worry about temperatures for them either.  Bluegill are good eating.

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