Gardening Rhythms

Choosing between Aquaponic Systems with Feeding Fish or Non Feeding Fish

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Choosing between Aquaponics Systems with Feeding Fish or Non Feeding Fish has its advantages and disadvantages.  We are not talking about  non-feeding fish.  All fish eat something.  The question is what?  Actually, the trade off comes down to your Nitrates.  In a non-fed fish tank, the fish eat the algae that grow on the walls of the tank.  Algae need to be exposed to light and it grows off the Nitrate in the water.  This means some of the Nitrate is diverted from your veggies and goes to growing algae.  This means you can grow about half of the amount of veggies and plants than a fed Auqaponics system.  The general rule of thumb for sizing your fish tank to the amounts of veggies grown is anywhere from 1:1 to 1:3 by volume.  In this case, you may want to consider ratios of 1:0.5 to 1:1.5 or 2:1 to 2 to 3 by water volume to grown veggie volume.

The advantages to a non-feeding Aquaponics system is you don’t have to feed the fish.  Your upkeep work goes down to zero.  The fish eat almost anything including the stuff on the bottom of the tank.  That is nice, but the system does not produce as many veggies as a fed system.  And you need to keep an eye on your algae growth and light exposure.

Picking Fish for Non-Feeding Aquaponics System:

 The type of fish for this application has to love to eat salads.  Yes, they need to be vegetarian or at least mostly vegetarians.  In think in this case, they would be vegan. 

 If you are interested in non-feeding Aquaponics systems, you need to pick only plant eating fish.  While picking fish, you need to pick fish that live at the same or similar temperature ranges.  A good combination is Feeder Goldfish and Tilapia.  Both fish eat algae and live almost in the same temperature range.  And the best part, they don’t each other.
The type of fish you choose will depend on where you live in the world and what is available.  In the case above, I can find cheap Tilapia fish in Asian markets.  I just bring in a 5 gallon bucket to the live fish counter and ask for Tilapia.  They will take the fish out of their tank and weigh it.  After, they fill your bucket up with water and dump the fish in.  Make sure you bring a lid or some sort of top with you.  In the drive home, the water has a tendency to slosh around and get your trunk or car seat wet.

When getting fish from the Asian market, they are often much stressed.  They may be compromised physically because they are in a strange place, the pH may be off and they are not fed in the super market.  Before putting you new fish in your Auqaponics system, you may want to give them a salt water bath to kill anything on the fish.  For more details see the chapter on choosing fish.

Feeder Goldfish is also a good choice.  They are very cheap; generally, 1 USD for a dozen fish.  They will start to eat algae right away.  If you system is outside and the weather turns cooler, they will go dormant.   This fish is great for climates where the tanks are outside and you receive freezing winters.  The fish will go dormant.  Just make sure to keep a small hole in the ice so the fish can get air.  It is possible for the Goldfish to die in frozen water because lack of air.

Feeder Goldfish grow to the size of your tank.  That means if you have a 300 or 400 gallon tank, your fish my reach lengths of up to 7 or 8 inches in length.   

• Gold Fish 
• Tilapia
• Veggie eating Carps
• Jade Perch
• Koi

 

Picking Fish for a Feeding Aquaponics System:

• Blue Carps
• Catfish
• Barramundi 
• Murray cod
• Trout
• Bluegill

For more detailed infomration on Fish Choices for Aquaponics, Click here

Getting a Non-Feeding Aquaponics System Started:

A non-feeding Aquaponics System needs to be exposed to a lot of light through out the day.  Since the system relies on light to keep going, It is best to make the fish tank out of tempered glass.  Algae go on the sides of the tank and the fish eat it.  This means the tank gets unsightly when fully operational.  You will be able to see the fish once in a while between the patches of algae.  If there are a lot of fish in the tank, you may have to place more clear glass in the tank to grow algae.  To determine if you need more surface area in the tank to grow algae, you can check your water quality and see if your veggies are growing quick or slow.  If your veggies are growing slow, you may not have too much light.  Check your algae population.  If you have way too much algae, increase the number of fish or reduce the light.  The Nitrates in the tank are begin eaten by the algae and are not available to the plants.  If your veggies are still growing slow, you may need more fish in the tank and more light.  More fish will produce more Nitrates for your plants.  Again, check the amount of algae on your tank walls, if it gets really “hairy” looking, you have too much light or not enough fish to eat it.  In general the top water surface of the tank stays clear.

Above: This looks like a really bad kept fish tank.  The sun is shining through the back and onto the glass tank wall.  The algae are kept to a short 1/8 inch from the wall by the fish.  If it gets longer, then there is too much sun or not enough fish.

 

Above:  Two gold fish eat the algae.  These two fish used to be less than 1 inch about 8 months ago.  They are about 4 inches in length.

In the past I have used 1/2 inch tempered glass for the tank walls.  Glued together with aquarium silicon dap.  You can not use the bathroom silicon dap from the hardware store; it emits a chemical after it dries that kills the fish.  Aquarium silicon dap can be bought in an aquairum store or a specility hardware store.  You will need several tubes.  They are sold as repair kits.  Here is a word to the wise about aquarum silicon dap, it takes about 1 to 2 weeks to dry.  That means the tank needs to stay empty for about 2 weeks after it is put together.  The dap has to completely cure to withstand the water weight pushing out the walls.  The other trick is to leave it clamped for the entire 2 weeks.  Also make sure there are no air bubbles between the edges of the glass.  It should be completely filled with aquarium silicon dap.  You can tell when there are no bubbles by looking through the covered layer glass.  Remember to put a metel frame around the top and bottom of the tank.  That glass walls will bulge out if it does not have support.  In general, 1 inch alumimum corner corner braces from the hardware store.

Above: 1 inch aluminum 90 degree support on the top of the glass tank.

Above: An edge shot where the bubbles are pressent in the aquarum silicon dap.  In a perfect joint, the whole seam is dark.  To the left of the seam is algea inside the tank.

If you choose not to construct your own tank and buy one, you can forget everything above.  The system I have currently is around 400 to 500 gallans.  The fish tank itself is around 350 gallons.  The rest of the water is in the pipes between the pond and the growing tubs.

The best place to put the tank is in the direct sun light.  If you live in a warm enough climate, you can put the system outside all year around.  If you live in a cooler climate, you  may want to move the fish in during the winter and outside during the summer.  For me, that is way too much work.  In this case, I would keep the tank inside and use several HID (high Intensity Discharge) lights to light the tank.  Low Pressure Sodium lamps give the right colors for growing algae and go easy on the pocketbook with the electric bill.

 Starting the nitrosifyers in your fish tank:

The process for starting a nitrosifyers cycle is the same for the Non-feeding and Feeding Fish systems.  The only difference is you need to keep the walls clean of algae by scrubbing and you need to feed your fish.  In the non-feeding Aquaponics systems, you need to feed your fish at first until the algae builds up enough.  Once the algae builds up and the fish are eating it, stop feeding them.

Place your plants in the growing tubs and add about 1/4 to 1/2 cup of liquid kelp.  You can get that at any hydroponic store.

For places to buy the liquid Kelp, Click here

 

 Further Information on Aquaponics Ecology:

 

Fish poop and pee in the water they swim in.  It is no different that walking through the air after someone farts.  In general that is ammonia for fish and methane for farts.  In nature is there is a cycle where body wastes are transformed into new building blocks for plants to use.  In this case, the fish ammonia is transformed into a Nitrite (nitrosifyers) .  The ammonia is transformed into a Nitrite (No2) by bacteria in the water.  (Nitrosococcus for Freshwater and Marine; Nitrosospira and Nitrosolobus for soils) 

 

Once the Ammonia is transformed into a NO2, then it is taken up by another bacteria to transform it into a Nitrate. (Nitrobacter for Freshwater, soils and Marine)  Now the ammonia is transformed into something plants can absorb and use to grow.  In the case of a Non-feeding Aquaponics system, some of the Nitrate is used by the algae for food.  The rest is used by the veggies.  This means the only energy coming into the system is from the sun light.  The algae grows, feeds the fish and the fish feeds the plants. 

 

The system cycle happens in the soil and in saltwater fish tanks.  The only difference is that fish in a saltwater tank are more sensitive to the amounts of ammonia and Nitrites in the water.  In traditional saltwater tanks, there have been elaborate methods developed to keep the water clear of ammonia and Nitrites. Once the Nitrates are too high, the tank water is changed.    It is unfortunate that most of the energy of that system is thrown out with the partial water change.  In one sense, you are throwing the baby out with the bathwater.  In the case described above, nitrates are used in plants, and the plants are used for fish food.

For more informartion on Cycles, Click here

Choosing between Aquaponics Systems with Feeding Fish or Non Feeding Fish has its advantages and disadvantages. 

 

This entry was posted on Wednesday, September 7th, 2011 at 8:29 pm. It is filed under Hydroponics/Aquaponics and tagged with Advantages, Aquaponic, between, Choosing, Disadvantages, Feeding, fish, Non Feeding, systems. You can follow any responses to this entry through the RSS 2.0 feed.