Comment

Comment by TCLynx on May 15, 2012 at 11:34am

Marty, a fine screen is going to clog easily.  I would go with a lower tech method, Like maybe the landscape fabric and a layer of some filter material or a shallow gravel bed and then into a well aerated drum/tank or whatever where the water is then sent on to the duckweed beds.

Right now I have an overflow that just splashes into a layer of the Zipgrow matrix media and through a stock tank with netting and the worms are all through the stuff!

Comment by marty lininger on May 15, 2012 at 10:15am

OK, i plan on filtering the water with 55 micron screen filter.  so, most of the remaining particulates would be pretty small.  is that still a suitable food for worms?

there would be no visible fish poop pieces.

also, keep in mind that duckweed wants ammonia, not nitrites or nitrates, so i have to be careful to not allow a process that converts ammonia.  i know what i am doing is pretty different from most other systems, it is my curse in life...

Comment by Carey Ma on May 15, 2012 at 9:35am

Thanks TC.

Yes Marty, TC has the right idea. I would process or mineralize the solids but not compost them as in traditional soil composting. The microbes in the worm guts and in the perlite break down all those solids into usable nutrients that plants can use.

I thought I posted a pic of my filter but can't seem to find it. Must have done it in one of my lucid dreams...hehe.

I am a strong believer in aeration so my layers of filter materials are separated with one inch air gaps, suspended by plastic boards with holes drilled in and a piece of  4mm landscape fabric. The first layer I already described~ splash rock on landscape fabric. Under that is about a foot of assorted course crushed rock/ gravel, landscape fabric, plastic board, air gap, a foot of perlite, landscape fabric, plastic board, air gap, another foot of perlite, landscape fabric, plastic board, air gap and finally a foot of sand. Underneath this are three layers of landscape fabric and landscape filter material, a final plastic board and air gap.

Large worms on top break down the chunks while smaller worms in the gravel chomp up any bits that manage to get by the first piece of landscape fabric. The rest of the landscape fabric in the lower levels are purely to keep the different medias separate. I love perlite both as a hydroponic media as well as microbe metropolitan/ colony. For the price vs ceramic aquarium bio reactors/ filters...its a no-brainer. I'm not sure why I have sand on the bottom but its there.

In my new system, solids run directly onto a splash rock that sits on some broken granite that is in a net pot, surrounded by soil. The idea here is to build up and retain as much nutrient as possible while increasing microbial activity. Excess nutrients are returned to the grow side of the AP system before circulating back to the fish.

I will offset this experiment with another raised bed using a microbial rich solution plus disintegrated fish poop as surface sprinkle to see which way produces the most beneficial microbes. 

Comment by TCLynx on May 15, 2012 at 7:33am

The duckweed wants the ammonia waste from the fish, the solids are not necessarily a benefit in the duckweed until they are converted to ammonia and other minerals.  I think Carey's vermi-digester or something along those lines between the fish tank and the duckweed tanks could be very helpful so you are not sending goopy solids directly to the duckweed and you can have worms work on the goop while also adding extra aeration to the water since duckweed does like aerated water.

Comment by marty lininger on May 14, 2012 at 7:43pm

Carey,

  if you consider that my main goal with the fish waste is to grow duckweed, then would you still compost the waste before it went to the duckweed pond?

Comment by TCLynx on May 14, 2012 at 7:02pm

I like the vermi-digester idea there Carey, I think I'm doing something sort of like that.  Just kinda by accident I have an overflow that goes through a big bin of filter material and the worms have totally gone nuts in the filter material.

Comment by Carey Ma on May 14, 2012 at 7:38am

Duckweed can be grown in two-inch trays instead of six inches, reducing your volume tremendously. Land area can be more efficient by growing them in stacked trays.

 

Yes pulverizing is a good idea, esp. if we can do it without using extra energy. However, it is also important for something to eat it (worms) to make it more soluble before it goes into and grow situation. I don’t know what your setup is like so can’t really comment but in general, the filter material should be porous enough to allow water to flow yet keep the particles out until they are eroded in small particles that will eventually be so small or completely broken down and passed through the filter system.

______________

Like I said before. It is best if we can find local sources of low cost organic input to determine what our best option would be. Meal worms, pill bugs, grasshoppers, crickets, little fish, waterborne grubs and larva are all good options to increase protein content.So what do you have lots of? Grass clippings, grains, surplus fish tanks, animal manures, food system byproducts, kitchen waste?

You might want to increase your symbiotic cycle to add another animal crop like Jon does to maximize the nute usage in his rabbit - fish - veggie system. We use cow urine  to supply our greenwater ponds. By doing this we reduce our feed cost by 4/5ths. In other words, we only feed our fish one pound of feed where we use to feed five pounds of feed. We could stop feeding our fish provided we reduce the population. So we use our feed to increase production and just to make sure they have the full range of minerals and vitamins. This year, instead of running our fish water through huge algae scrubs and filters before it goes through DWC in PVC pipes, we are running it directly to our raised wicking beds before it circulates back to our ponds.

Comment by Carey Ma on May 12, 2012 at 5:59pm

Great conversation folks!

I must butt in here. I think bio digesters are wonderful and have a place in home/ farm life but I'm not sure I agree about using it to mitigate fish solids, which will eventually end up in the soil garden. What I did was send it to those that love it most..my earthworms. I have a piece of geo textile or landscape fabric that covers the top of my 50 gal drum filter/ bio reactor. Incoming water is splashed onto a block of granite, aerating the water and breaking up the larger particles. These particles are quickly gobbled up by the earthworms providing a smashing smorgasbord for the colonies of microbes. And out comes highly usable nutrients for whatever plants one choose to grow.

Although it is more troublesome, I believe in using a variety of feed inputs vs mono-crop. It is relatively easy to keep fish alive but to provide a feed that truly enhances their well being, I believe requires diversity. In my experience. It is mostly about pegging the protein level one desires to give their fish at different stages in their growth cycle, provided you use natural products as input.

As for what type of form you choose to feed your fish, whether floating or sinking depends on what kind of fish you choose to raise. Feed mills that make floating pellets are about twice the price compared to ordinary pellet mills, esp for smaller mills. The main problem I think independent feed makers face is how to dry the initial stock. I believe a dry stock is necessary to increase the potency of the feed. To me, feeding raw/ unprocessed duckweed would be more like eating salad rather than steak.

@ Jon: Way to go man! Rabbit/ fish AP is a wonderful choice and example of integrated bio systems for urban/ peri-urban food production...as long as you can buy pelleted food for dem bunnies. Which brings me back to making our own feed.

Unless we do it purely as a hobby where time, energy and money are not true factors, it is probably impractical for most with clear water aquaculture to make pelleted feed...unless there is enough demand where some sore of feed co-op is formed. This isn't said to discourage anyone, just my opinion at present. I believe we should start a chart so we can have at hand information so each of us can build our feed formulas according to what we have available in our local environments. What commercial/ semi commercial operation around you produces organic "waste"? What can you buy or grow and process relatively cheaply? 

There has to be a source of input before we can withdraw. Algae, duckweed are great but where do they get their feed from. How many solar Jules of sunlight does it require to produce one gram of flesh? At present, feed is the crux that prevents AP to become sustainable. Again greenwater AP is about as natural and efficient as one can imagine, however, there still needs to be a continuous, low cost input source.

Oh BTW, I have a wonderful bio digester for sale if anyone is interested. It'll cost around $700 plus shipping from Seattle. Duel purpose pellet mills start around $2,000. Floating mills @ $4,000 and up.

Comment by TCLynx on May 12, 2012 at 6:01am

Marty, you might want to research bio-digesters then as a way to break down the waste quickly and hopefully keep the solids from interfering with the growth of duckweed.

Comment by marty lininger on May 12, 2012 at 5:54am

TCLynx

if the original calculation is valid and the water is 6 in deep, then we are talking about 18,000 gallons of water under this duckweed.  that is a lot of volume to absorb the nutrients and there will be slow recirc movement. 

i am considering pulverizing the waste before it gets to the duckweed so breakdown is fast and solids buildup minimized

the point is to grow duckweed as fast and efficiently as possible and stinky mess  must be engineered out

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