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Aquaponics and Fish Feed

March 1, 2010

Several times a week I get asked some variation of the following question “OK, so if aquaponics is sustainable, what do you feed the fish?”. Just happened again yesterday at the hair salon.

Here is the deal. Fish, like birds, reptiles and mammals, need a range of protein based on their species. Each species typically fits somewhere on an omnivorous spectrum ranging from piranha’s that eat protein almost exclusively to largely vegetarian fish like tilapia and carp. The protein that fish typically eat in the wild is….other fish. When we started raising fish in captivity (aquaculture) fish feed was carefully crafted by nutritionists to offer the optimal amount of protein (fish meal) to quickly grow each species of fish depending on where it was on that omnivorous spectrum.

“Where is the problem in all this?” you may ask. Well, the problem is with the fish meal. As I’m sure you are aware, we are overfishing our oceans at an alarming rate. In March 2009, the Food and Agriculture Organization of the United Nations reported that over 70% of fish species were currently endangered. Another study published in November 2008 in the Annual Review of Environment and Resources found that one-third of the world’s marine fish catches are ground up into fish meal. A study published in the journal Ambio reported that in 2006, aquaculture consumed 57 percent of fish meal and 87 percent of fish oil. We simply can’t keep using ocean caught fish to feed our farm raised fish.

We can avoid all these issues by just raising vegetarian-leaning fish on garden waste, duckweed, black soldier fly larvae, worms, etc. The reality is, however, that raising enough food so you can feed your fish….so they can raise your food… takes work, and space and most of us are short on both of those. I admit that I’m looking for the convenience of a commercial feed in a form I can feel good about. I suspect many of you are too.

There are several organizations currently developing alternative protein sources for fish feed. In an article by Rebecca Nelson in the latest edition of the Aquaponics Journal (issue #56, Q1 2010) three companies creating protein sources were highlighted. At Ohio State University aquaculturalists are exploring the feasibility of using soybeans to replace fish meal and plan to soon test the product on yellow perch. Scientists at the Agricultural Research Services and Montana Microbial Products have teamed up to produce a barley protein concentrate that can be fed to trout, salmon and other commercially produced fish. Finally, in Idaho Springs, Colorado Oberon FMR has just signed a deal with Miller-Coors to turn 5000 tons of beer sludge into 6000 tons of fish food flakes.

But all of this is being developed as commercial feed and will only be available to aquaponic gardeners if we demand it. I called Oberon a few weeks ago and asked them when their feed would be available. They said that it was still in test, but once it was available it will only be available if the feed packagers request it, who need it to be requested by us. Just for grins I called one of the feed producers Oberon thought might be interested in pelletizing and producing a vegetarian fish feed and they said “sure, we’ll do it, but it is a special order that we only do in 5000 lb batches”. Oh, and it only has a 6 month shelf life.

Is aquaponic gardening sustainable? Absolutely. It uses very little water, enables organic food growing in areas that couldn’t otherwise grow, and naturally recycles fish waste as plant nutrients. But we need to do better with our inputs.

The solutions to the issue of using fish meal are on the way but let’s insure that solutions are available to all growers of fish, not just the large commercial operations. The only way we are ever going to see aquaponic gardening reach it’s full potential as the easy, sustainable growing technique I know it to be is to demand an easy, sustainable way to feed the fish. Demand it!

8 Comments leave one →
  1. john thompson permalink
    March 1, 2010 11:17 am

    I was just struggling with this last night. I have trout in the backyard and just moved some indoors to my basement set up (they are gorgeous!). Mostly to avoid the mercury inherant in processed fish foods, I’ve been looking for ways to get out of the fish meal cycle. It’s not fully functional yet, and is probably destined to be more hobby sized than anything, but here’s what I’m experimenting with now:

    I’m rearing live-breeders in the basement. I started with half a dozen guppies in October. I now have probably 400 fish (though most are still small). This is in a simple 100 gallon stock tank, with heater, and a simple hydroton filter. I’m not sure what the limits are for production, but it looks like it could sustain quite a trout population when all the babies start breeding.

    Then the question becomes “what to feed the guppies?” I think brine shrimp, which are inexpensive and easy to grow and as pure as your water supply is probably the answer. I’m exploring high output/low time ways to grow them in sufficient quantity. I know someone has figured this out before me.

    Ideally, I want a live breeding vegetarian for my feeder stock (duck weed grows like a, uh, weed, and would make ideal food input). But I haven’t found one yet. Anyone know of a small, prolific live bearing vegetarian fish?

    On the other side, tilapia will grow on a veggie diet (they love zuchini and duck weed) just not as fast as if they were fed protein. In a hobby system, I’ll gladly trade growth rates for healthier, more sustainable inputs. I have plenty of duckweed growing for anyone local! BTW, it’s edible too, and makes a nice, fresh green salad topper. My 7 year old loves it, but so far he and I are the only ones brave enough to try it.

  2. March 1, 2010 6:23 pm

    5000 lb batches… I wonder whether some aquaponics entrepreneur might make such a purchase, break it down into smaller units, and resell it to smaller-scale aquaponicists. The reshipping costs would probably make this prohibitively expensive over the long term, but maybe it could help demonstrate the viability of the market so that the producer would start thinking about retail possibilities.

    I also wonder about that six-month half-life. If desiccated pellets are stored in the dark, what kind of spoilage takes place over that time scale?

    • March 1, 2010 7:12 pm

      That would be great if an entrepreneur took that on – sign me up! They did say that the life of the pellets could be extended if they were refrigerated…but that is a mighty big fridge in my book!

  3. March 2, 2010 1:57 am

    Very good and thoughtful blog. I enjoy reading your various posts on Aquaponics issues. I think its only a matter of time as more and more people discover Aquaponics that suppliers will make a sustainable formula for our needs. We discuss your ideas over at Murray Hallam’s Forum at
    Drop on by and say hello.

    • March 2, 2010 7:10 am

      Thanks for your kind comments, Castaway. I agree that soon we will be a large enough market to warrant a sustainable brand of fish feed. Meanwhile, let’s make some noise! I will come visit Murray Hallam’s forum soon. I’ve never met Murray, but I’m a fan.

  4. March 20, 2010 8:36 am

    What to feed them is a problem I have had for a long time.
    I have had this problem with breeding seahorses and other marine animals. What to feed them, without breaking the bank.
    And I am an organic gardener with my own compost pile for tea and soil amendments.
    And now I am looking into aquaponics, So my question is WORMS, do they have a fast growth rate to keep up with a growing stock and will Tilapia like them?
    Most important is TIME. Growing the food to feed the animal/fish/coral can consume as much time if not more as rasing the animal/fish/coral for show or your food.

    • March 20, 2010 2:18 pm

      Charlie, you are absolutely right in your observation – you could spend as much time, space, energy and money raising the food for the fish as the fish. That is why I’m such a fan of trying to push the feed developers to make a feed that we can feel good about – the convenience of purchased feed is undeniable. That said, yes, tilapia like worms and it would be a great enhancement to their diet. They also like vegetable matter (lettuce and buggy broccoli leaves are favorites of mine), duckweed, and black soldier fly larvae. I’ve come to believe that the best diet for an omnivorous fish like a tilapia (or any omnivorous creature, for that matter) is a varied one that includes some amount of commercial feed as an insurance policy that your fish are getting the vitamins and essential amino acids they require.

  5. Dean permalink
    May 28, 2010 1:19 pm

    Enjoyed your article. I manage a feed mill and due the nutritional work for the company. I have a small aquaponics set up and am looking at moving to a commercial scale. I think that the Tilapia would do well with the plant based proteins. One thing that needs to be looked at would be the fat profile in the farmed fish after being fed these diets. The fish oils in the feed give a very healthy fat profile in the farmed fish. That being said the fish meal can lead to things like PCB and other heavy metal accumulation. In our area we could achieve a 40% protien pellet with a balanced amino acid profile for around 15 cents per lb. We plan to try some in the coming months but several things need to be looked at before commercial sale could be possible.

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