Backyard Aquaponics
A place to discuss aquaponics

I had some to understand Les' autosyphon, and now you all throw this in. Les - going to have to explain all this to me on Sunday. I too plan cascading beds. Four beds in total, 2 at one height and 2 at another.

Best I bring pencil and paper then

Bring google sketchup Les - since you are so good at that

Having minor eye problems

Use the redundant backup system Les ... other eye

Update - I have redesigned my proposed system for a number of reasons:
1- The area I am putting it on is the Southeast corner of the house, where I have an erosion problem, therefore I will need to put up a few retaining walls anyway, so... Why not put something behind them?!
2- I was having some issues with the dual alternating autosiphons. Not that I don't think I can get them working, I just don't know if they are worth the trouble in this area.
3- If I build them as three cascaded GBs, I can make them part of the landscaping, and not something that neighbors will complain about.

See my sketchup of the plan.

I have a big drop of 7'6" (2.4m) going around this corner, so I'm breaking it up into 3 terraces.

Cool!

So the fish tank is the bottom one, right?

Awesome.

Yes, the big one on the bottom is the fish tank. Each of the 3 beds is approximately 4X4X1 (1.2mX1.2X.3m) with the tank being about 3X as deep. My plan is to use a pond liner over some blue styrofoam pver gravel. The overall sixe will be approximately 1350 L with about the same volume in GBs- that way if the pump fills all beds simultaneously, the water inthe tank should be at least 1/2 full. If we can get the autosiphons to sork properly, we'll only drain the tank 1/6 of the way. My plan is for slow drain / autosiphon / overflow so that if everything works perfectly, we'll be running an autosiphon, but if the autosiphon has problems, we can move to a timer with slow drain. Since the beds are cascaded, we would need to fill all 3, so we need the overflow.
I drew the walls as nice, square ones, but I will actually be using some landscaping blocks that will make the walls more curved in the corners. The walls will also not be vertical, but raked about 1:4. So the drawing is not exactly what it will look like....
Also I'm planning on putting the same pea/drainage gravel around the tops of the beds, so it won't be entirely clear where the growbeds start exactly, That should make the aesthetics of the whole thing more pleasing.

So what are the rules on tilapia outdoors in NC? Do you have to demonstrate that they can't get away?

I believe that's what the inspections are for. Although my area is probably going to be too cold for them to survive for long in the wild.

My thoughts are that in order to ensure I don't contaminate the local waterways with Tilapia, I will do a few things:
1- have a filtered "overflow" pipe. Before the water runs over the side of the tank, I will have a standpipe with overflow at the max water height for my tank with a filter to keep out small fishies. So that if, for some reason, I get a large influx of water, I will be able to dump fish-free water onto my lawn.
2- I am planning on building a GH over my beds. The sides would be up during the warmer weather, but closed up during the winter.

I think if I can demonstrate the ability to keep Tilapia out of NC waterways, (BTW, they would have to swim across about 20m of grass, then another 50m of wooded area before they could get into the waterways anyway, so that may not be a major issue), that I can get the permit.
I'm hoping to get started on construction in the next few weeks, and I could always start my future harem in my 34-gal aquarium if I crank up the heat a bit.... The current tropical residents may get in the way, but not for long, the Tilapia would probably not mind them much - they might have the current residents over for dinner! I may also end up doing a small indoor salad-under-lights setup for that area....
-Doug

Thinking like an inspector....
Clumsy heron swoops in, grabs a brooding female, and flies straight to the nearest body of water. It drops the fish who releases her spawn.

Just something to think about. I also agree that NC would be too cold for tilapia to make it through the winter. However, 'goverment' and 'logic' do not always belong in the same sentence. Before you build something really grand, you might talk to someone to see exactly what they would consider sufficient.

PA is waaay colder, and it's still illegal for me to release them!

Yeah, the heron scenario is one of the reasons for the greenhouse even during the nicer weather. Ideal situation is always have plastic roof, but use shadecloth when its warm, and 2-layer plastic when its cold.
I also want to look into bees (with an interior and exterior exit to the greenhouse and the world at large), I'm still wanting to play with sprouts as a source of food for the fishies, but still need to have an automagical way to make it happen, even if it's batch-based automagic....(thinking) Anyway, that's what I'm planning to do above the fishtank, probably using some combination of pumps, timers, and buckets/sieves.

Okay here's my third plan, and the first one to actually go into production:

It uses 3 window boxes joined on a split pvc pipe with autosiphons, and sits on top of the fish tank. The main filtering is happening in the undergravel filter, but there are gravel beds for the plants. It is only 4-5" deep, (10-12cm) but the purpose was to show my wife that the system could look decent.

I have 15mm chipped marble as the substrate, with a thin coating of pearlite on top to keep the seeds from washing down. The biggest problem is some of the pearlite washes into the aquarium and I have to net out some pearlite.

This is sooo cool to see the plants grow!

I hear they are a resourceful fish

Your water should be nicely bufferd! Marble is also CaCO3 !