Tilapia Harvesting Day

One of the benefits of an aquaponics system, of course, is raising edible fish.  Ideally, the fish should grow quickly and be efficient at converting the food they eat into body mass.  It also helps if the fish are hardy and can adapt to changes in their environment.  Having a mild taste that many people find appealing doesn't hurt either.  Tilapia meet this description, so it is no surprise that they are a favored species of aquaponists.  The only downside to raising tilapia that I can see is they are tropical and cannot survive in water temperatures below about 50 degrees Fahrenheit.  This can and does present a problem for anyone attempting to raise them in a temperate climate.

Where I live in the central United States, the first frost usually comes around October 15th.  But as you might guess, nighttime temperatures begin dipping into the 40's by mid-September.  This change in seasons pretty much dictates the ideal harvest time for any tilapia that are being raised outdoors.  Even though we've already had several overnight lows in the 30's. the lowest the water temperature ever got in the tilapia pool was 54.  That's primarily because a large volume of water acts as a heat reservoir.  This enabled me to delay harvest day until the first weekend in October.

The method I chose to dispatch the fish prior to gutting them was to immerse them in ice water.  This kills them within a few minutes, and seems pretty humane to me.

as easy as netting fish in a barrel  :)

I have read that, in most parts of the world, fish are traditionally cooked whole.  That is, head intact.  Evidently the exception to this practice is my own culture, presumably because we Americans prefer our meat having as little resemblance to a previously-alive animal as possible.  I suppose on some level I can understand how folks might find staring into the eye of a fish they are about to consume somewhat creepy.  But neither I nor my wife have any such reservations, and since not having to filet all these fish meant the cleaning process would be much quicker, I opted to go with the rest of the world on this.  I should also mention that, in addition to there being edible meat in and around the head that would otherwise be wasted, some people believe leaving it on improves the taste of the whole fish.  Not sure if I'm buying that one, but as they say, the proof is in the pudding.

My dad passed away when I was a young boy, so I never had the opportunity to learn many things that fathers teach their sons.  One of those things was how to clean a fish.  Fortunately for me, today we have the internet and you-tube.  I am constantly amazed at all the regular folks who take the time to record and post helpful "how-to" videos online.  What an incredible resource for do-it-yourselfers!  So... after watching a couple of people demonstrate their technique for gutting and de-scaling a fish, I was ready to tackle the job.

I was surprised how easy it is, really.  After a short learning curve, I was down to five minutes per fish.  That was at a slow, careful pace.  I'm sure I could do it in two or three minutes if I rushed, but I was in no hurry.  And yes, I'm sure there are those who can do it in 10 or 15 seconds, but I had nothing to prove.  One thing is for certain, it beats hand-plucking poultry feathers!

a small 2-3" incision

the chickens enjoyed the entrails

lots of scales... hoping the chickens eat these too - a good source of calcium for eggshell production

In total, I processed 41 fish.  I fileted the last one just for comparison.  I read somewhere that if you filet a fish, you end up with about 30% of the whole.  Add in a lack of experience and, well, my result was probably closer to 20%.  Yet another reason to go the "cooked-whole" route.

these were vacuum packed in pairs after freezing solid

My wife used THIS recipe to prepare two of the fish for dinner that night.  I don't know if it was the fact that they were so fresh, or the seasonings they were cooked with, or that they were raised from babies right here on the farm, but we both agreed that they were the best tilapia either of us had ever eaten.  Seriously, you should try this recipe.

One fish apiece was more than enough to fill us.  It was a little work picking out the bones, but no big deal; certainly worth the time saved in cleaning them.  The skin was delicious, and at the end of the meal we had just a small pile of bones left which will eventually be used to make fish broth.

One note of interest:  I thought I had about fifty fish, total, before processing.  As it turns out, my estimate was low.  After harvesting 41 of them, I still have about 30 adults left.  The remaining fish are all indoors in the IBC tank, so there are no worries they will be killed by the imminent colder weather.  I will probably do one more harvest in November, and that should be it until next summer.

Our freezer is now well-stocked with tilapia.  As my aquaponics operation expands in the coming months, my plan is to raise about 500 mature fish per year for our own consumption, to be harvested quarterly.  I've got close to that many fry swimming around in aquariums out in the garage right now, so barring any catastrophe, that plan has already been  "hatched".  :)  Stay tuned for further developments.  Don't forget you can click on the pictures to enlarge them.


from this:

to this:

(in approximately 12 months) 




That top picture was taken on June 1st 2013.  Two of those tiny guys ended up in the lower picture about a year later.  You can read the story of how those fish were raised to maturity HERE.

The Beginning

Aquaponics -  a food production system that combines conventional aquaculture (raising aquatic animals such as snails, fish, or prawns in tanks) with hydroponics (cultivating plants without soil) in a symbiotic environment. In normal aquaculture, excretions from the animals being raised can accumulate in the water, increasing toxicity. In an aquaponic system, water from the aquaculture system is fed to a hydroponic system where the excretions are broken down by nitrogen-fixing bacteria into nitrates, which are utilized by the plants as nutrients. The water is then recirculated back to the aquaculture system.

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It was early in 2013 when I first learned of Aquaponics, stumbling upon the topic while browsing the internet.  Intrigued, I thought I would give it a whirl, since the concept seemed to fit well with my family's goals to be less-dependent on the grocery store for our food, and to better control the quality and freshness of the food we eat.

In early May I purchased about 100 tilapia fry (baby fish) from a farmer near St. Louis for $20, and thus the adventure began.  Initially I placed the fish in a small 10-gallon aquarium.  While they grew, I prepared for the next phase of the experiment.  I built a 4' x 8' grow-bed out of 2 x 12's and plywood, locating it outside on an existing unused concrete slab.  It was filled with about 30 cubic feet of pea gravel purchased from a local quarry for $10.  An 8-foot diameter x 18" high kiddie pool from Wal-Mart ($15) would hold the water, about 500 gallons of it.  A small 45-watt 550 gph pond pump from Amazon for $35, a few pieces of PVC pipe and fittings, and everything was ready.

The weather had not quite warmed enough to safely move the fish outside, so I used the time to begin "cycling" the system by introducing a small quantity of ammonia into the pool water daily.  This simulated the presence of fish and provided food for the beneficial bacteria that would eventually colonize the gravel bed and later convert the actual fish waste (which would otherwise build up to toxic levels and eventually kill the fish) into relatively harmless nitrates.  It took about 2-3 weeks for the beneficial bacteria to set up shop in sufficient numbers.  The seedlings I began planting in the system consumed the nitrates they produced.  Once the water chemistry was balanced and steady, it was ready for the fish.

The tilapia moved to their new pool-home in late May.  It was none too soon because they had out-grown their 10-gallon tank weeks prior.  The fingerlings continued to grow quickly over the summer months, as did the vegetables in the grow-bed.  In order to determine which kinds of plants were best suited to growing in this system, I planted a wide range of normal things you would find in a typical garden: cherry tomato, bell pepper, string beans, eggplant, zucchini, and various lettuces and chard.  I even had a corn stalk in there for a while until it blew over one day in a thunderstorm.  I replanted it in the soil garden and it survived.  Everything in the grow-bed did very well, but I came to the conclusion that any plant needing trellising or staking would be easier to manage if growing in dirt, or at least at ground level.  Besides, my wife and I eat lots of salad greens, so why not stick to that for the grow-bed?

Click on the pictures for full-sized versions.  This was how last year's grow-bed looked by mid-summer.  The 100' coil of black irrigation tubing in the foreground is a makeshift solar heater to warm the pool water when needed.  About half the output from the pump is circulated through it on sunny days.  I am currently using a garden hose for the same purpose.

Eventually autumn came and as the temperature dropped, it became evident that the fish had not grown large enough in five months to provide decent-sized filets.  The decision was made to keep about half of them over the winter in aquariums, inside the house.  The other half became dog food (our three canines are on a raw meat diet).  I snagged two larger aquariums on craigslist, a 55-gallon and a 30-gallon, with pumps, heaters, and various accessories, for about $100.  As it turned out, that was not enough space for fifty 6-inch long fish, so I temporarily re-purposed two large plastic storage bins as auxiliary water tanks.  This was still not enough room, but would have to do for awhile.  I needed to change the water in all four tanks about twice a week all winter long, even while feeding the fish a subsistence quantity of food.  What a bother!  It was clear I needed a new plan.

In January I began enclosing a corner of my detached 3-car garage.  A 10' x 10' room gradually took shape.  Lumber, insulation, drywall, and plywood purchased from Home Depot for the project came to about $400.  I already had most of the electrical and plumbing parts on hand, including the proverbial (used) kitchen sink.  To house the fish, I bought a quantity of used, food-grade, 275-gallon IBC tanks for $60 each.  I kept two of them and re-sold the rest at a small profit, so mine ended up costing a mere $15 each.  Gotta love craigslist !  A small $15 space heater from Wal-Mart had no problem maintaining that little room at 80-degrees.  I didn't even notice a bump in my electric bill.  A rusty old 4-bulb fluorescent light fixture that the previous homeowner left behind in the barn as trash was cleaned up, re-painted, and now provides sufficient light for the interior grow-bed plants.

I am about to add a second grow-bed to the left of the one in the picture.  Also, a second IBC tank resides under the test kit in the picture and is currently empty, but will be put into service this winter.

I moved the fish out to their new home in February of 2014.  The grow-bed I built for that small room in the garage was only 2' x 4' and way too small for the amount of waste the fish generated.  As soon as the weather got warm enough in mid-May, I moved half of the fish (about 25) back out to the pool and replanted the outside grow-bed with lettuce, spinach, and chard.  The inside grow-bed was STILL too small for the remaining 25 adult fish, so until I get around to building another bed, I have to use an improvised filter system to catch most of the solids before the water enters the grow-bed.  The heart of this filtering system is a used 55-gallon plastic barrel bought for $10.  A valve in the bottom of the barrel enables me to drain the solids off periodically.  The solids are used as fertilizer in the soil garden, so nothing is wasted.

The plants in this interior grow-bed are thriving.  After some experimentation to determine which plants would do best growing under standard fluorescent lights, I settled on "swiss chard / perpetual spinach" from Baker Creek Heirloom Seed Co.  This variety lives up to it's name... we have been clipping leaves since April and the plants just keep producing more and more.

This is about how much chard we get per picking, which we do about once a week.  Vigorous growth, healthy, bug-free plants... what more could you ask for?  Not bad for something grown inside under artificial light.

Sometime around mid-July, I noticed a few baby fish had gotten caught in the filter floss.  Upon closer inspection, I discovered there were hundreds of fry swimming around with the adults in the pool.  My fish were finally breeding!  I quickly got the three previously mentioned aquariums up and running again, and transferred several hundred fry to these tanks.  I built large filters out of used plastic buckets and 4" PVC pipe to handle the waste.  These fish are growing fast and will become next year's crop.

Oreochromis Aureus... aka Blue Tilapia... the most popular fish raised by aquaponists.  After having raised them myself, I understand why.  They are a very hardy breed.  As long as you don't let their water get too cold, they will tolerate just about any other mistake a novice fish-keeper can make.  Daily temperature swings from 70 to over 100 degrees, wide-ranging pH levels, low dissolved oxygen, turbid water conditions... my guys have seen it all and manage to live and procreate!



Also, in anticipation of needing more space for the new batch of fish as they grow, I have purchased two additional 35-gallon aquariums off craigslist for $30 apiece.  Each one of these is sub-divided into three 12-gallon spaces, each partition with its own "through-the-wall" plumbing.  These six units will enable me to segregate the fish according to size until they reach about 3"-4" long, at which point they will be transferred into the IBC tanks.

What a bargain.  These tanks used to be part of a fish display in some Wal-Mart somewhere.  I bought them from a re-seller on (where else)... craigslist !



More space is needed to accommodate all these aquariums and to provide for future expansion.  I decided to enlarge the "fish room" inside the garage by enclosing an additional 6' x 10' of floor area.  The plan is already in the works and I should have the material to begin construction by October 1st.  This 60% expansion will essentially become "the nursery", with various aquariums and their attendant filtration systems on dedicated shelves.  That will allow me to re-claim the counter space currently being occupied by the fry tanks.  I also want to try my hand at vermiculture.  From what I've read, adding worms to aquaponic grow-beds will enhance the efficiency of the system.  We shall see.

Stealing another six feet.  I already removed the OSB that was covering the insulation.  It will be re-used on the addition, as will the door you see in the picture.



It is currently late-September (2014) as I am writing this blog entry.  The 17-month-old adult fish are about a foot long, on average, and now ready for harvest.  This must happen before the end of the month, since local overnight temps have been dropping into the 40's pretty regularly.  By circulating some of the pool water through about 200' of garden hose on sunny days and keeping a solar blanket over the pool during the night, I have been able to keep the water temperature above the danger zone.  Tilapia are tropical fish and are stressed at water temps below 60, and cannot survive at all below ~ 50 degrees.

The netting over the pool prevents hawks from grabbing an easy meal.  I haven't lost a single fish to predation yet.

it's what's for dinner!  (soon)

Once the freezer is stocked with filets, and as the new generation of tilapia grow into fingerlings, they will eventually be moved into the empty IBC tanks.  Of course, much smaller fish generate much less waste, so hopefully the existing grow-bed, combined with a second one I intend to build shortly, will provide ample filtering through this coming winter.  Additionally (and conveniently), one of the exterior walls of this "fish room" faces due-south, so my plan is to build a 16'-long x 24" wide grow-bed outside along the wall and plumb the IBC fish water to and from it through the wall.  This will more than quadruple the grow-bed volume I currently have for the IBC tanks, and will enable me to grow a wider variety of plants next season.  It should also eliminate the need for additional mechanical filtering of the water.

This is what the outside grow-bed currently looks like.  in the foreground is "May Queen" butterhead lettuce, almost ready for picking.  Behind that is "Parris Island" romaine-type lettuce, (some heads already consumed).  And lastly in the background is more Swiss Chard - Perpetual Spinach.  All these varieties have grown well without the need for supplements or any special care whatsoever.



There is also room for more grow-bed space on the concrete slab.  The plan is to build a 16' x 4' bed adjacent to the existing one and thereby triple the space for plants and pool-water filtering.  Hopefully this will be done in time for next spring.

I will post a new entry here in about a month when the new "aquarium addition" is finished.