DWC... has anyone been successful with it in a smaller backyard system and is it worth the go? 

This monday I will be finishing my 2nd 3'x6'x16" gravel growbed and I'm trying to decide if its worth adding a small DWC to complete my system for the time being. 

The order for the DWC would be as follows: Pond - Swirl filter (completed) - Bio filter (completed) - Floating Raft - back to pond via overflow. 

DWC system would be about 100gls. 

Any thoughts about this? Is it worth the go? 

If so, what should I focus growing? We love fast varieties of lettuce, strawberries, spinach, chard. to name a few.

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No kidding.  I use an indexing valve with timer to flood and drain 6 beds.  

Vlad Jovanovic said:

Sam you can always use a timer (timed flood and drain) if you're not diggin' the auto-siphons...


Yeah, I too use an indexing valve with a quality repeat cycle timer to flood 8 media beds in sequence...siphons just seemed like they'd be a potential finicky nightmare and not worth the cost benefit (to me at least). 

Hey Vlad, You convinced me to use timers and indexing valves but I got this strange looking cloud hanging over my grow beds when I went out to the GH after dark. Is this normal??



Vlad Jovanovic said:

Yeah, I too use an indexing valve with a quality repeat cycle timer to flood 8 media beds in sequence...siphons just seemed like they'd be a potential finicky nightmare and not worth the cost benefit (to me at least). 

That's awesome Jim...all you need to do is figure out how to harness some of that, to power the new (likely stronger) pump you'll need for the index valve...Again, it's all about set and setting...and what the operator wants out of the system...

I pay about 3 cents a kWh and rely on my GB's to feed my 546 square feet of rafts with a consistent flow rate...so I'm not about to dick around with auto-siphons. Now, if I wanted to live off grid, or if my electric were more expensive, or I was just trying to grow some stuff for my family, I'd probably just use the auto-siphons (actually, as far as siphons go...the loop siphon is my favorite). Again, it's all about set and setting and what you want 

Hey I'm all about automation. Sorry I just couldn't resist

I just picked up a Mitsubishi PLC for nutt'n and I am looking for a good program and a cheap indexing valve source or plan for making one. Not a priority but that nifty PLC is drawing me in. As I recall it has 12 in and 8 out. It's a 20MR. My son has the pc software so I can write my own if need be. I also have 2 dish actuators that could open roof vents, etc. Amazing what you find in or on the way to the dump

Vlad Jovanovic said:

That's awesome Jim...all you need to do is figure out how to harness some of that, to power the new (likely stronger) pump you'll need for the index valve...Again, it's all about set and setting...and what the operator wants out of the system...

I pay about 3 cents a kWh and rely on my GB's to feed my 546 square feet of rafts with a consistent flow rate...so I'm not about to dick around with auto-siphons. Now, if I wanted to live off grid, or if my electric were more expensive, or I was just trying to grow some stuff for my family, I'd probably just use the auto-siphons (actually, as far as siphons go...the loop siphon is my favorite). Again, it's all about set and setting and what you want 

Meanwhile, back at the DWC farm...  

I'm moving further and further away from having anything floating on top of the water, but instead having the 'rafts' become 'tables' (for lack of a better term)  and set the height of the water below the table by cutting the overflow downpipe to the correct length, and resting the tables on the edge of the DWC trough.

Now my challenge is to find something that will suitably span a 4 foot growbed at a reasonable price.   I've tossed around a lot of ideas but the current one is fiber cement siding or backer board.  

Does anyone know whether this stuff will stand up to use as a net-pot table above a DWC trough?   It should be water resistant enough given it's intended uses.   It may need some support underneath which I'm thinking of 1/2" PVC pipe with occasional legs descending to the bottom of the trough.  There are also some possible challenges in cutting holes for the net pots.

Is there anything nasty in the composition of cement fiber board that I wouldn't want in close proximity to my fish and vegies?

I'd love some input and feedback.  Much appreciated.

Hey John,

Outside of the weight issue they are pretty inert. You may want to inquire about any fungicides.

I have a carbide hole saw that I use for tile flooring that should make easy work of all those holes. There is a fiberglass reinforcement that you could seal with epoxy around the holes and edges, Check the ceramic tile section for cutting tools. I would say they should last forever but try and find the lightest weight board as you will need to get under it now and then. Let us know how you make out as I am about to make some of the same decisions on my next 20ft row.

Another issue I worry about with the just above water system is the fungus gnat hangout potential.

Check out the indexing valve with modified stem.  I use a 60 watt pump and it works just fine.

Vlad Jovanovic said:

That's awesome Jim...all you need to do is figure out how to harness some of that, to power the new (likely stronger) pump you'll need for the index valve...

How big a system? and where should we look for such a valve or Google it?

George said:

Check out the indexing valve with modified stem.  I use a 60 watt pump and it works just fine.

Vlad Jovanovic said:

That's awesome Jim...all you need to do is figure out how to harness some of that, to power the new (likely stronger) pump you'll need for the index valve...

TC sells them. (The way I designed my system ratios I needed more flow and a bigger pump anyhow...so I went with the 'normal' low flow disk/stem assembly instead of the gravity modified version...let me try and find you her link...

Here you are... http://www.aquaponiclynx.com/products/aquaponic-systems-and-compone...

Jim Fisk said:

How big a system? and where should we look for such a valve or Google it?

George said:

Check out the indexing valve with modified stem.  I use a 60 watt pump and it works just fine.

Vlad Jovanovic said:

That's awesome Jim...all you need to do is figure out how to harness some of that, to power the new (likely stronger) pump you'll need for the index valve...

Backer board is really weak, probably weaker than foam. Glen Martinez of Hawaii uses regular plywood sealed with Cabot stain. Plywood is cheaper, and much stronger, and in my opinion better. Cement will also raise pH with water contact, and the cement board gets much heavier and weaker when wet. I have used regular boards to span a grow bed, with good results. They cup from the relative moisture below amd the dryness above, but they work fine. Paul Trudeau has been experimenting with recycled campaign signage.



John Malone said:

Meanwhile, back at the DWC farm...  

I'm moving further and further away from having anything floating on top of the water, but instead having the 'rafts' become 'tables' (for lack of a better term)  and set the height of the water below the table by cutting the overflow downpipe to the correct length, and resting the tables on the edge of the DWC trough.

Now my challenge is to find something that will suitably span a 4 foot growbed at a reasonable price.   I've tossed around a lot of ideas but the current one is fiber cement siding or backer board.  

Does anyone know whether this stuff will stand up to use as a net-pot table above a DWC trough?   It should be water resistant enough given it's intended uses.   It may need some support underneath which I'm thinking of 1/2" PVC pipe with occasional legs descending to the bottom of the trough.  There are also some possible challenges in cutting holes for the net pots.

Is there anything nasty in the composition of cement fiber board that I wouldn't want in close proximity to my fish and vegies?

I'd love some input and feedback.  Much appreciated.

After lurking around on this forum for a while and asking some questions, I've bitten the bullet and built a 4'x8' DWC trough and tables/rafts.  See the photos.

What I really need to know now is, what media do I use in the pots?   I'm giving lava rock topped with pearlite a try, but I'm not sure that'll work.  What is everyone else using in the pots?

P.S.  The third photo is my horizontal version of the 'Nash Blaster'.  Thanks to Rob Nash for a good concept that got me out of a tight spot, literally. 

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