Food for Tilapia

There are several options for feeding your tilapia depending on the size of your operation and the format of your grow environment.  This entry will focus on systems that have the fish in enclosed tanks.  This is as would be found in a city backyard system.  For reference, the use of large outdoor ponds is a different system that has other options.

General feeding issues.
You want to feed your fish for maximum growth and least waste.
Your fish can go with less food or no food for a couple days.
It is better to underfeed than overfeed when you will be away from your setup.  Overfeeding will lead to water fouling and fish kill.
Feeding your fish too much will result in undigested food travelling through their system, and inefficiency.

Starting:
If you are just starting; you have "started" your tanks and you are awaiting the delivery of your fingerlings; these are good places to get food:
http://premiumfishfood.com/
http://jimsfish.webs.com/fishfood.htm

Once you are going, you can experiment with different foods.  You can grow your own algae, make your own food or even use kitchen scraps.  Be slow in scraps you put into your tank to ensure you don't foul the water (eg. oily muffins are bad, bread can be good if used in moderation, raw vegetables can be good).  I found tofu to be a welcome food by the fish.

Ongoing and Recipe for your own food:
Purchased bulk food:
A good, reasonably priced food for your grow tanks is Purina Game Chow.  This is available locally at Tractor Supply Company.  It is variably sized and works well with both my auto feeders.

Tofu:
Tofu can easily be made at home. The most difficult part is making soy milk, but you can do this easily now with "soy milk cookers".
An example of a good maker is here,
SoyJoy Soymilk maker
Once you have made soymilk, you add a coagulant (calcium sulfite, or magnesium chloride) put in a press to remove excess water.  You can get food grade ingredients from http://www.soymilkmaker.com/order.html

Further instructions are here,
http://www.soymilkmaker.com/making_tofu.html

Cream of Wheat Cakes:
While I was investigating making my own tofu, and pondering the coagulants used in that process, I began experimenting with alternate recipes.  What I settled on and use regularly is the following. It came from the thought of making tofu, but instead uses other readily available ingredients.
1 cup instant Cream of Wheat
1 cup of medium burr ground soy beans
1/2 cup of ground corn meal
1/2 cup of finely cut dry seaweed
Begin making the instant cream of wheat per the package instructions.  Immediately after pouring in the cream of wheat, also add the ground soy beans, corn meal and dry seaweed.  Continuously stir so it remains smooth and does not burn.  Once the mixture begins to thicken turn off heat and cool for about 10 minutes (until still able to pour, or scoop).  I scoop the mixture into used tofu tubs with a spatula, pressing as I go, and then allow to further cool.  Cover with plastic wrap and place in refrigerator.  To use, cut rows and columns into block so that you can remove a square column and feed to tilapia.

Automatic feeding:
I use two types of auto feeders.  I use smaller units for my 55gal and 110gal tanks, and a larger unit for my 300gal outdoor setup.  Both feeders dispense 2-3.5mm circular pellet food (the Purina Fish Chow).

For my indoor tanks I use an Eheim Air Feeder.  These provide about a week of capacity and are reliable. I have a complete review here,
Amazon Review
Purchase from Amazon

For my outdoor grow out tank I use a Super-Feeder ASF-1 unit. I have modified my unit with an extra carrier to hold a little more than 1 week of food.
Super-Feeder Fish Feeder

Reference:
http://seagrant.uconn.edu/whatwedo/aquaculture/pdf/ncrac114_tilapia.pdf
Aquaponic Gardening by Sylvia Bernstein

Aquaponics:fouling water and other problems

Problems to be encountered in Aquaponics systems:
* predators: raccoons, opossums, they will eat your fish or destroy your grow beds looking for snails
    --> mechanically protect: cover fish tanks, enclose system
    --> simple styrofoam has shielded my system from these predators, though they did cut through my plastic door before I put foam on it also

* sludge fouling your piping and grow beds
    --> use a sludge separator: http://wolfenhawke.blogspot.com/2012/09/aquaponics-sludge-separator-update.html

* water fouled: this could be for any number of reasons, but most likely it will occur from overfeeding.  This can happen accidently due variations in an auto feeder
    --> turn off all feeding until water clears, don't worry, your fish can survive days without food
    --> if you see excess floating food, remove it
    --> if possible replace at least half of your water, but don't fret it if you cannot replace
    --> if you are using a timer on your water pump, bypass it so it is running 24/7
    --> run the system continuously until the water clears -- it will, then restart normal operation

* mysterious fishkill:  your fish are dying but the water is not cloudy
    --> this is rare for tilapia farming
    --> check your chemical levels
    --> check for dead fish fouling the water
    --> check the tank temperature -- sometimes heater elements will fail on
    --> check for water getting too cold -- temps lower than 55F are bad for Tilapia
    --> proceed similar to water fouled actions above: but on chemical imbalance, you will also need to investigate -- this could happen if you didn't "start the fish tank" and you put a lot of fish in at once, see http://wolfenhawke.blogspot.com/2012/10/starting-fish-tanks.html

 

Starting the Fish Tanks

First of all, a little primer on fish tanks.  They are an ecosystem creating a nitrogen cycle.  The fish eat food and expel nitrogen and feces which decompose and create more nitrogen.  There are two types of bacteria that live in a healthy fish tank that convert the nitrogen first to nitrites and then to nitrates.  Too much nitrogen or nitrite in the water will kill fish.

The filter in most fish tanks does a little bit of mechanical filtering, but it's primary purpose is to house the bacteria that is essential for the nitrogen cycle.  Thus if you thoroughly wash your filter every week because your water is getting cloudy, then you are in a constant wash cycle and are not getting your fish tank where it needs to be for your fish to be healthy.

You can read more here:
http://www.diyaquaponics.info/bacteria.html
http://fins.actwin.com/mirror/begin-cycling.html
http://www.algone.com/articles/aquarium-filtration/nitrogen-cycle

Nitrates are readily absorbed by plants for their nutrient uptake. This is the lynch pin in making aquaponics a self sustaining ecosystem.

I started my aquaponics tanks using clear ammonia and putting some extra operational filters from my indoor fish tanks into the aquaponics tanks (for bacteria transfer).

Monitoring Aquaponic Grow Bed Water Levels

With ebb and flow water systems, it is useful to monitor your water level under the surface of your grow media.  This is a simple but effective method do that.

As you are filling media into your bed, put a length of 1.5" PVC pipe in the bed vertically in the media.  Allow the top to protrude above the media surface by a good 2 inches (5cm) at least.  If you are using fine media, it would be good to attach some fiberglass screening with plastic lock ties at the bottom of the pipe.

Now make the indicator using a straw and a piece of styrofoam that is smaller than the diameter of the PVC pipe.  Say about 1.5cm in width.

 Picture showing styrofoam with straw embedded.  Note the graduations marked on the straw.  This is long because I use deep grow beds in my setup.

Picture showing the level meter in operation.  Water filling the grow bed is causing the indicator to rise.

Salads with Ebb and Flow? YES!!

In aquaponics systems, salad greens are normally grown in a flow or flood system with the roots continuously in running water.  I have a deep bed ebb and flow system and recently populated one bed with mesclun salad mix seed.  I used the vermiculite bed for the salad greens.  Please see http://wolfenhawke.blogspot.com/2012/10/aquaponics-grow-beds-and-media-stackup.html for various media stackups.  Seeds were just spread on top of the fresh vermiculite.

The following picture is a successful yield offered by this method.

Bell Siphoning for Aquaponics Grow Beds

Aquaponics systems use one of two water recirculation systems primarily.  One method is the "flood system", "flow system", or "constant flow" system.  This system runs the water continuously through the root systems of vegetables.  The other method is the "flood and drain" or "ebb and flow" system.  This system adds water to grow beds causing the water level to rise to just below the media surface, and then drains the water and repeats the process continuously.

Flow systems are good for salad green farming.  Flood and Drain systems are good for all types of vegetables but are a little more complex.

As you have seen from my setup schematic, http://wolfenhawke.blogspot.com/2012/10/single-pump-aquaponics-system-design.html, I use Flood and Drain in my system.  This is accomplished by using a bell siphon in the grow bed.  This apparatus does not use energy but counts on vacuum created in a sealed water system.  There is plenty of information on building your bell siphon.  One paper is available here, http://www.ctahr.hawaii.edu/oc/freepubs/pdf/BIO-10.pdf.

Since my grow beds had a drain plug on the side, I used this. I do not recommend going from the side as the setup is more complex to tune, but I am showing this for interest/information.  Certainly, you can setup your similar beds with the draining straight down.

As you can see, my internal standpipe makes a 90 degree bend which is non-standard.















After that the bell pipe is installed on the standpipe.  Note, one disadvantage with the 90 degree standpipe connection, is that the bell pipe cannot seal as far to the bottom.  The top of the cut at the bottom of the bell pipe determines the minimum level of water in the grow bed.  My bed will have about two inches of water always at the bottom.

After this stage, you can fill the planter with your media.  As you can see, one benefit I do have with the 90 degree install, is that I can tune the height of the water draining by turning the bell pipe and standpipe as a unit.  I had to do this on all my planters to get the desired height -- this is likely because I do not use "snorkels" on my bell pipe and the trapped air is compressing and affecting the rising water level.

Single Pump Aquaponics System Design

I use an architecture in my aquaponics setup that requires a single pump per fish tank used.  This minimizes electricity and vastly reduces the complexity of the control system.  The water is pumped to my sludge separator design (see blog for details) which is at the highest location in the system.  Gravity is then used to move the water from the separator to the grow beds and back to the fish tank.  Using more than one fish tank in the same system requires balancing the effluent water from the grow beds and this will be addressed in another article.

The schematic of the setup is shown below:

The fish tank is shown below:

 













The sludge separator is shown here.  The pipe on the right is the influence. The pipe protruding from the front is the overflow back to the fish tank (a safety measure).











Here the piping is shown from the grow beds (3/4") to the collector (2") which returns the cleaned effluent back to the fish tank.

Since I use flood and drain as my water distribution, I could technically just keep the water pump running. I use drains on the side of the grow beds.  This side draining is much less efficient than bottom draining and what happens is that the water slows down in draining as it gets to the bottom of the bed.  This causes an equilibrium to be reached if the water pump is left on all the time.  At equilibrium the water is about 1/3 depth in the grow beds at all times.  I alleviate this problem, and save electricity to boot, by putting my water pump on a timer that runs 30minutes on, 30minutes off continuously.  This means I only pump half the time. It also allows the grow bed to get flooded and drain once per on/off cycle.

I have not had trouble with the side draining, but it does take a little tuning of the bell siphon.  We will cover this siphon design on another article.