Aquaponic Gardening

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I'm looking for some feedback while my system cycles up.

 

Here's what I've been up to over the past few weeks:
 
System: As you can see in the attached photo I set up an aquaponics system in a greenhouse (it’s a tent, really).  It has a 55 gallon blue barrel for the fish and several grow beds using expanded ceramic media (hydroton) with flood and drain valves for plants.  There is a sump on the far end of the left trays.  The system is currently cycling in preparation for establishment of fish and plants.  I have several ideas for additional beds in this system.  I have a 300 watt aquarium heater in the fish tank simply to keep the water above 65 in the cold.  The past few mornings I’ve found the water temp to be above 60 despite ambient temps around freezing.  This “greenhouse” has screened windows and is under an apple tree.  I’m hoping the leaves will provide suitable shade in the summer to keep things from getting to hot in the summer.   Unfortunately I do not really know what the water temperatures will be through an entire year here in Reno.  The tent isn’t insulated so it’s a gamble if left outdoors in the winter.  Even during the summer the weather can fluctuate 40 degrees in a 24 hour period.  I’m thinking there will be roughly 70 to 80 gallons of water in the final system.   Eventually I’d like to convert the pumps to solar and I’d like to have herbivores as fish so that I can produce the bulk of my fish food in the greenhouse (duckweed assumedly).  The grey plastic cube on the right will propagate duckweed for fish food.  The whole idea is to have input to the system be as small as possible but output be significant.  (Current input has been a bunch of money to set this up!)
 
Fish: Generally aquaponics systems surround tilapia which are intended for food in addition to the vegetables created in the system.  I’ve found that Tilapia are illegal in Nevada as they are considered an invasive species and according to my friends at the Nevada Department of Wildlife, this is non-negotiable.  Tilapia have done significant damage to the native species in Nevada.  I’ve been thinking of alternatives to Tilapia.  Edible Fish are generally carnivorous, fickle about water temperatures, and slow growers.  My thought is to use Koi for the first year to see what happens.  As to the Input/Output objective I have troubles believing the idea that buying small koi and selling large koi is a very viable business model.  Although my objective would only be to break even.
 
Questions/Assumptions I'm currently pondering:
1) Stocking Rate – I’m thinking 3 to 4 fish with hopes they grow quickly
2) Duckweed
a. What percentage of feed can be duckweed? 60/40 with pellets?
b. What would be the best source for duckweed?
c. Is there a better plant than duckweed for Koi? 
3) Koi
a. Is there actually a local “market” for selling a couple large koi after I’ve raised them? 
b. I’d assume there might be if they were somehow special or somewhat rare.  
    i.   I'm not sure what to look for when thinking of “special” koi
    ii.  How special would they need to be? 
    iii. Where would I get them?  D & S Koi Farm?  Aquarium Store?
    iv.      How much should I expect to pay for “special” koi?
c. I've read several web sites and books on koi ponds and have a general knowledge.  Any suggestions specific to:
    i.   My system?
    ii.  Local issues (weather, etc)?
    iii. Preparation?
    iv. Other folks doing something similar in the area?
4) Other species that might be better?
 
Lots of information;  Lots of questions.  Hopefully not too many because I'll be under way in a week or two!

Note: Reno is a weather zone 7.  It's not a great place for plants!  Winter temps are usually below freezing.  We can get a hard frost as late as June or as early as September. Summer days can get above 100F and then drop to 60F in the same night.  At Altitude of 4,600' the sun works really well!  Typical Humidity is around 10 so evaporation is a problem.  We get about 7 inches of rain a year on average.  All that said, a cheap greehouse with lots of water keeping temps consistant MIGHT be a solution.  We'll see.

 

Thoughts?

 

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To keep temperatures stable you will probably need to go quite a bit bigger.  The blue barrel may be ok for some goldfish but trying to grow out large Koi for the specialty market, you would definitely need to go much bigger.

Here in my central Florida location, I like a 300 gallon fish tank as a minimum size for temperature stability.

300 gallons is also the minimum size I would try to grow out channel catfish in.

As to food fish being too carnivorous or finicky about temperature, naw, tilapia are over rated and they are the ones picky about temperatures (if you want to grow out tilapia fast, you need to feed them better protein feed than the channel catfish need.)

Channel Catfish and Bluegill are the fish I chose for my systems since they can stand the cold and if you get the system cycled up ahead of time before getting the fish, they are pretty darn easy.  Now I admit that I haven't done well with them in small tanks but in the bigger tanks they have been very easy.  Now you won't be feed them mostly duckweed but so far I haven't heard of anyone who has managed to grow lots of fish or veggies using only or even 50% duckweed.  Remember, if you are growing duckweed in the system, it will be using up the nutrients and you won't have as much left over to grow your veggies so again, you reduce the inputs and it will reduce the output.  If you can grow the duckweed using some other nutrient source then this might work but again, it takes a lot of space to grow a lot of duckweed.

FYI, in many places, koi carp or goldfish would be a "food fish too"

Thanks for the info!

Couple items - 

Size: As you'll note I have just about everything on wheels and its all in a 6x8 tent.  This is a temporary do.  garage?  basement?  Lighting costs for some tomatoes?  I'm resolved that this project is going to freese in the winter.  Its a question of extending our growing season, really.  That means the fish either perform a function by November or become fertilizer for next years flower beds.  I could be wrong.  We'll find out.

 

Fish: "FYI, in many places, koi carp or goldfish would be a "food fish too""  Yep, I been there.  No thanks!  We're picky Brook Trout people up here at high altitude! :) Bluegill might be an option though!  I'll do a little more research on them.  Again, temps are entirely unpredictable here.  Snow on Fathers Day is just as likely as a 100F scorcher.  I suspect I'll go cheap and to get a couple/three koi and just see what happens.  The secondary market for Koi curiosity is more of a "just wondering" thing at this point.

 

Duckweed: hm.  I was thinking I could use compost from the rest of the garden/kitchen/compost bin to get the nutrients for duckweed (?).  Let me know if this makes sense - the greenhouse will need get a couple more 55 gallon barrels for thermal mass anyway.  Using them to grow duckweed in the summer and possibly for composting for a little more warmth in the winter.  I'll have to rethink the feed percentage though.

 

Thanks again!  I'm reading everything I can get my hands on.

 

There is plenty of reading to do.  But there are people at altitude doing year round aquaponics in solar greenhouses so it is possible, but you would probably need to go a bit larger than your current tent, but it should work for a starter/learning system in any case.

Ya know this hobby is kinda addictive so it's hard to stop at just one system anyway.

By the way, bluegill are good eating and they survive in lakes that freeze over in winter so if you can keep the water from freezing in your system, you can keep a system ticking over slowly through winter even if it is mostly dormant from Thanksgiving through Easter.  If it is going to freeze, you can probably shut down and just keep enough aeration in the fish tank to allow some free water on the surface for gas exchange and probably keep fish alive even if the system is otherwise shut down.

Duckweed news flash.... Dr Rakocy reported that in a study he did fish fed a diet of all you can eat duckweed lost weight over 30 days.

update:

Well I'm finally cycled.  it was much faster than I expected.  I'll skip the gory details of a lesson learned save to say uh... please age your pee if you go that route.  I decided to dump all the water and start over with fresh tap water (yes, a little chlorine sounded like a good idea).  nuff said.

 

I Added a couple more grow beds which are giving me some hydrological head aches. one of them is half a recycled 55 gallon barrel which I cont think is food grade.  Its set up as a si gle barrelponics deal but im just using the top part right now.    this sucker is probably coming out of the system soon.  I've over estimated my ability to deal with all the quirks in flow control and I'll need this thing to self manage itself while i travel for business.  the wife can feed fish, but if its a big liquid messnobody is going to be able to wobble this or change that easily for me.

I've got three neat fish in the tank now  I went for Shubunkin goldfish.  I was advised that koi would grow too large in such a small tank.  Shubunkin max out at about 12 inches so they wont get too big for the barrel. Resell?  unlikely.

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