Backyard Aquaponics
A place to discuss aquaponics

sorry Ryan, I don't have a link to any particular study on the 50% duckweed thing. Heck I expect that Dr. Rakocy's study may have triggered many other studies to figure out how much duckweed could be used before the weight loss happened.

On a side note since it isn't aquaponics to grow veggies but green water culture of tilapia or other filter feeding fish can provide very low cost feed. New Alchemy Institute did research into solar algae ponds growing tilapia way back in the 1970s I think. Primary input for that is to get the translucent tanks, good water supply and some sort of fertilizer to get the algae to bloom. (sun doesn't provide the nutrients, only the energy for photosynthesis so some form of fertilizer input is still required though the algae can be quite good at converting the raw materials in to the necessary feed for fish like tilapia.)

i've tried growing minnows in tanks, and have hatched a couple hundred, but they're slow growers.. i have "green water" cultures going for the baby minnows..
i've had 3 pretty good size hatches of crayfish that have gone in the big tank to feed my perch and bluegill, but they don't all get eaten, and will continue to grow/reproduce in the big tank.. i clean duckweed out of the small tanks 1x a week or so and put it in the big tank for the tilapia to eat.. yellow perch and bluegill won't eat much duckweed..
i've got a couple of scud cultures going as well.. glass (or grass) shrimp haven't been very prolific for me..
but my main fish food is still the commercial feed i buy from a store that orders the 50lb bag for me (less then $1/lb)

Just an additional question. I´m on board for the idea of commercial feed as it would be the best for the fish and spare the owner time and work + it would bump up the crops.

What i want to ask though is about the trace elements and the iron...

My parents sometimes spread out a little bit of ashes in their veggie patch and especially around the fruit trees to supply some more of the trace elements. How would that work for balancing AP? (If you really wanted to try an all-homemade feed which would not supply this)

And for the iron, and here i come stomping it without knowing a fraction as much as you guys but... I myself have quite poor hemoglobin values (iron in red blood cells) and several times i came across articles about (brace yourself) roman soldiers who put iron nails in their wine (so that the iron level in the wine would raise) to raise their hemoglobin values after blood loss.

The simple point of this story, i have been scratching my head wondering if throwing in some iron nails (or other iron rubbish, and of course remembering where you put them!!!) into the GB would help raise the iron value in AP in the same was as adding egg shells can take the edge of in acidic water.

Anyone ever tried? (metal scrap is always lying around anyway)

Humbly
/H

Rusty nails, or iron.... produce ferric (Fe3+) ions... not the form of iron that plants can uptake... which is to ferrous (Fe2+)... such as found in chelated iron...

This doesn't really mean the iron can't be used but it must be converted first - some plants have the ability to do this using phytosiderophores or are associated with bacteria that can do it for them.

But aren't phytosiderphores primarily grasses...

And iron converting bacteria are (from memory) usually related to suphur... and anaerobic process... and denitrification....

Think this was all discussed in Janet Peltiers RSG thread... ("really smart guy")...

Yes as far as I know on the phytosiderophores this is correct.

I remember reading that thread but it's been a while. I took a look back at this and it looks mainly focused on the anaerobic conversion process.
- On the other hand, there are lots of aerobic and facultative anaerobic bacteria with the ability to take Fe3+ out of the environment using siderophores and convert it to Fe2+ within the cell. From what I could find, no anaerobic environment outside the cell is needed. How much these bacteria help the plants they are associated with although some plants are certainly helped by this association.

I do know that bacterial concentrations are higher in and around the roots of plants, than they are in most of the soil. I suspect that most of these bacteria have siderophores because useable iron is in short supply.

Cheers

To put it simply... No...

However you can grow the vast majority of your feed on the farm. Here is a link to a vegterian fish food for Trout: http://www.ars.usda.gov/Main/docs.htm?docid=21911 Note there are two versions of the formula on the page, one which uses fish oil, and one which uses a plant and Algae alternative.



Just an aside as others have pointed out the reasons why that doesn't work in AP. Straight Iron intake (even supplemental) is poorly absorbed by the human body. By far the best source for Iron is within the diet as it is then introduced in a why that the human body can easily absorb and use it. Livers and Lean red meats, (meats in general really though red meats tend to have a bit higher concentration of Iron) are the best source for easily absorbed and used Iron. The next best is plant sourced Iron, while it is absorbable and useable by the body, it does not absorb as readily, nor is it used as easily as animal based iron sources. Inorganic forms of Iron (such as in nails) are basically unuseable by the human body. Iron is one of the many elements that we require to live, in which we are unable to make use of in their inorganic form.

Here is the "Really Smart Guy" Thread http://backyardaquaponics.com/forum/viewtopic.php?f=8&t=1523&hilit=really+smart+guy

Note on the ashes!!!!!! Important here. Ashes are useful but be careful. They will raise your pH!
Ashes can provide potassium and likely some other things but they are also how people used to make old fashion potash lye or potassium hydroxide. They would leach the ashes and then dehydrate the result. Lye is caustic and it can injure you and if used willy nilly could really mess up your AP system. (once had some one insist that ashes could be used with no worry of overdosing apparently because their grand ma used them in the garden without measuring, so they dumped like the whole fireplace bucket in their aquaponics system and couldn't figure out why the pH was off the charts and all the plants were looking horribly strange and purple.)
That said, I know of people who do leach their ashes to make their own pH raising solutions but they do it carefully, I would recommend doing some more research into it since I've never done it personally so can only offer cautions that handling lye should be done with care.

If your onsite soil is very good and balanced then perhaps you could manage to grow more balanced ingredients for your home made fish foods, however, you can buy feed vitamin/mineral admixtures for making your own fish feed if that is what you are planning to do. Most of us are not lucky enough to have perfect soil (if we did, we might never have discovered aquaponics.)

The problem is that in these systems, you are trying to maximize the amount of food production in a minimum of space. A decent population of catfish will need acres in the wild to have suitable habitat for what they do. But a large pond has an ecosystem that includes amphibians, smaller fishes, insects and plants. And the state still stocks game fish so that people can go down and fish enough out of it to make dinner a few nights every summer.

If you are worried about sustainability, don't forget the costs of buying all your fish. Theoretically, the same amount of fish feed is getting used whether you are growing it yourself or buying it in the store. It's just a matter of how many other resources are invested into that fish by the time you raise it, pack it and ship it cross country.

Dana

Once the new transgenic varieties DHA and EPA omega 3 containing oilseeds of canola and soybeans hit the market (2016 in Australia), it will be more than possible to feed for very negligable cost. Its more a function of whether you have the land available to cultivate these grain crops or if you live close to agricultural areas, then you will be blessed with omega 3 rich grains for (at current commodity prices) 60c/kg for 40% oil canola or $1.50/kg for 20% oil soy. North Americans will be the first to benefit from this trangenic application. Many will struggle with their aversion to GMs but in the end economics always wins, particularly as the global debt crisis worsens. All this stimulus has simply kicked the can down the road.

No, economics doesn't always win... We do not need GM crops and I will continue to refuse to buy any product containing GM crops. When will we realise that sometimes we just aren't smarter than nature.

Um yes it does and yes it always will, in the end. Careful, you are a retailer and some customers may not alway agree with your ideology. They will simply go elsewhere.

And before you dismiss this technology as having no value, can you please explain to us all how aquaponics and aquaculture can continue in their current form if fish meal supplies dwindle to a trickle? There are many inconvenient truths in the feed inputs of AP that also indicate 'we just aren't smarter than nature'. That was a good one by the way. Almost brought a tear to the eye.

I certainly wont be putting any GMOs into my system, just as I dont buy any GMOs to eat myself. There are enough like minded people around such that someone will produce products to meet the demand... at least until the big multinationals have polluted all life with GMOs...

Industry Races to Get Green, GM Omega 3 from Plants
by Stephen Daniels
1 August 2006

Industry giants are locked in a 'fish oil arms race' to develop genetically modified crops that could challenge the supremacy of fish as the best source of omega 3 fatty acid, with both BASF and DuPont reporting progress in the field.

<b>Fears about dwindling fish stocks coupled with the putative risks of pollutants from oily fish, </b> have pushed some in academia and industry to investigate the extraction of omega 3 from alternative sources ...

http://www.nutraingredients.com/Industr ... rom-plants