Wednesday, April 20, 2011

Duckweed and Tilapia


Tilapia Tank

 Now that the weathers warming up, I thought i'd mention my next project, raising tilapia.  It actually started about three months ago when I bought about 20 fry (baby tilapia) from a hobbiest is St.Augustine.  Since they need temperatures above 60 degrees, I had to keep them inside, in our utility room actually, in a in a food grade 55 gallon barrel.  Right there next to the washing machine and my beer brewing equipment, good fun.
  Tilapia are ideally suited to backyard aquaculture because they are extremely hardy.  Given a warm climate they will thrive in conditions that would kill most other fish species.  They are prolific breeders, and perhaps most importantly, can eat just about anything; be it algae, plants, insects etc...  This is particularly important from a sustainability perspective since you don't have to feed them commercial blends packed with fish meal (ground up fish, which depletes our oceans),or grains grown using fossil fuels and shipped long distances.  In fact, simply dropping a burlap bag filled with some chicken manure in their tank will help 'seed' the water, causing an algae bloom, which the fish then eat.  Nothing goes to waste, another closed loop!
  What I found particularly interesting is their affinity for duckweed.  If you've ever seen a pond covered in what appears to be green slime, it is probably duckweed.  A prolific weed, it is considered one of the fastest growing plants on earth.  If that weren't enough, it is also highly nutritious, with a surprising amount of protein, even more than soy, which is similar in quality to animal sources.  And in a world beset by rising oil prices, it can also be used as a fertilizer.  You can even feed some to your chickens, with some sources I found saying it can make up nearly 25% of their diet.  Duckweed is even a great source of food for humans, though despite some enticing recipes, i've yet to work up the courage.  But to return to our subject, tilapia can survive when fed exclusively on duckweed.
  So here's what i've done.  I bought a $15 kiddie pool, filled it with water and a few scoops of chicken manure.  Then I just needed to find some duckweed.  While there are online sources, I thought  i'd avoid paying for it and find a wild source that is already adapted to our area.  I first remembered that there were tons of duckweed at the jacksonville zoo, used to feed some of the animals.  Sure enough, I found some clumps of it in a ditch beside the road just outside the zoo, having probably escaped by sticking to the legs of a bird.   Took that home, dumped in the kiddie pool, and waited.  For the first first two days nothing much really happened, probably the shock of a new environment.  Then, voila, it was off like gangbusters.  True to what i'd read online, it began to literally double in mass every 24 to 36 hours.  Id simply go outside with a little aquarium net, scoop off half the surface, and by the next day it was full again.
  By this point i'd moved the fish outside under our pear tree, to a 400 gallon plastic tank.  Now normally this would be prohibitively expensive, and defeat the whole purpose of saving money on food.  But with a tip from a friend, I was able to find a local container business that offered damaged tanks at a deeply discounted price. Mine had about a 3 inch hole in the bottom, easily patched using silicone glue and a bike tire repair kit.  The fish, many of which are now nearly 6 inches long, seem to be thriving.  Every now and then, if the water appears hazy, I drain some of it into our vegetable garden.  Free organic fish poo fertilizer!
  In another 5 to six months they should be big enough to eat.  I already have a ton of recipes in mind, i'm especially keen on trying some filets sauteed in homegrown basil and meyer lemons.  And though my only olive tree (i plan on buying more) is still far too small, in the future perhaps we'll have olive-encrusted tilapia.  And finally, i'm hoping to experiment with salt-curing them.  From what i've read, this is an excellent way to prolong their storage, so that we will have fish to eat throughout the winter months.


  1. Wish I would have read this before I threw away the above ground pool

  2. lol, you'll know for next time. its never too late!