DWC ... Floating Raft...

[Nathanael]

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.

[Bob Vento]

Actually I want to grow various leafy veggie such as lettuce, spinach, chard, etc. so I would like a few rafts in operation.
Plus Marcia & I have immediate family whom I am sure will take the excess produce off of our hands if need be.

I like the idea of the morter tubs. Home Depot sells them for around $13 each here is a link http://www.homedepot.com/h_d1/N-5yc1v/R-202086174/h_d2/ProductDispl...

and the size seems good as well. What do you think Rob?

[Rob Nash]

 

Rob Nash's  Hybrid Design – 300 gallon

 

 

 

-The stand pipe and the water line in the FT are the same. About 18 inches.

-the Media beds are on 3 cinder blocks and the DWC Rafts are on 1 cinder block.

-there is only about 4 inches from the bottom of the media beds to the top of the raft.

-the polisher is a 30 gallon tuff tank from Tractor Supply Co. with orchard netting.

-with the FT in the ground at least 12 inches, you will have a 22” water level.  Not mandatory.

-pipes don’t have to be in-ground.  

       

FT In Ground – 300 gallon

 

-this is the preferred option. Less materials and better insulation.

- shown with 4’ x 16’ x 16” raft @ 14” water depth

-water returns over the fish tank edge at 14”

-both of these systems would have two 4’ x 8’ media beds = 64sft and two 4’ x 16’ x 16” rafts = 64sft

-the Nash blaster(air release tube) under the siphon, is necessary on both.

[Jon Parr]

Nathanael, I am using redwood 1"x12" boards coated with epoxy. Plywood with paint would be fine too, but I'm trying to avoid any possible leachate from paint and glues. I have 1" air space between wood and water. For quick leafy greens I don't use net pots or media at all. I use starter plugs made by International Horticulture, made from fir bark, and they look like brown sponges. They are cheap, 2.8 cents each, and very easy to pop out of trays an into boards. When harvesting, the plugs get cut off and get thrown into the compost pile along with the roots, or sold with lettuce head as live-root plants. Another product called Ellepots are also good, and about the same cost.

I gathered gammarus from a local creek, by the thousands, with a stainless steel mesh colander. You can also buy them. I know of a lab in San Diego and one in Sacramento that will mail them to you. I also sell them, but low on stock right now.

Rob, great diagrams. I use a combination between the two, with a fish tank on the ground with SLO, gravity flow to polisher, gravity flow to rafts, and pump from the raft back to the tank (no media in that system). I do this because the raft has the cleanest water (least pump maintenance), and the biggest sump volume (least vertical fluctuation)

[John Malone]

Hello Rob,

You're in-ground tank diagram above is almost exactly where I want to end up with my system.

I currently have 2 grow beds of 6'x4' and a 500 gallon in-ground fish tank.

A couple of questions:

1) What is the 'polisher'?

2) What is the 'Nash Blaster'?

Thanks

[Rob Nash]

John,

the polisher is a 30 gallon tuf tub with orchard netting in it.

flow into the bottom and out the top... it serves as a final filter to 'polish' the water before entering the rafts.

the 'nash blaster' is to the return pipe under the grow beds that the bell siphon drains into. my intern named it that, because he insisted i take credit for coming up with it... at least as far as we know.

its just an air release pipe, with out it you will have air lock issues and the siphon will fail.

its a 4" section of pipe installed on the 2" drain pipe. This provides a place for the water to drain w/out splashing out of the pipe ...which is not glued to the bottom of bell siphon.

NOTE - by not gluing it to the drain pipe (or 'tail pipe' of the bell siphon), it allows the air to escape when the bell siphon 'bottoms out'...this allows you to set your plumbing on the ground or bury it.. i like to bury it and go back into the fish tank through the sidewall.

 

[Vlad Jovanovic]

Rob, how often do you clean the netting in the polisher and "how dirty" does it get in said time?

And so that your answer means something... it'd help to know what your stocking density is and of feed rate...and the brand/type of feed might be a nice tidbit as well.

A 16'x4' raft, assuming there's about 10" of water in there is about 400US Gallons...4'x8' x12'  media bed minus displacement minus distance from the top holds...what, about about 180US Gallons?...I'm just curious, how big's the fish tank in that particular system?

Sorry for the barrage of questions...I was contemplating using something similar before my nursery trough...

[Jim Fisk]

Here is a pic of one of my ibc gbs converted to a raft bed as another option. I simply remove the bell siphon and plumb the same drain over to the corner and up to the depth you want. I put a protective cover on the spillway drain and you're set to go (after a biofilter or gravel bed prepares the fish water of course)

And here is a graphic of the biofilter I am about to add for the next 5 gbs:

[Jon Parr]

Jim, that's an interesting bio-filter. I understand that the pea gravel adds surface area and traps solids and floaters for further break-down. I also understand that airstones, especially submerged in gravel, plug quickly and require cleaning, which would be hell to access in a dirty double bucket of gravel, solids, and slime. May I suggest replacing the gravel with bird-netting? It would be quick and easy to pull out, to access airstones and do any maintenance.

[Sam Burton]

I've actually gone primarily to rafts and wicking beds.  I am not very handy and have a terrible time getting auto siphons to work.  It's my on ineptitude.  Raft systems are easy for me because I can make swirl filters easy enough and I add some filter balls in to aid the bio filter.  Also the rafts themselves are excellent biofilters (the walls and undersides of the rafts).  Since I already have 40 or more Earthbox self watering containers, I divert water from the sump when I need to top up the containers.  I don't overdo the stocking density, so I don't really do fruiting plants in the rafts (though I can get awesome growth of tomatoes in the early stages then transplant them into the containers.  Also, I have the solids as fertilizer for the beds and for fruit trees.  I will continue to work on building a flood and drain that actually works.  I don't have the cash flow to buy a kit.  Until then, what I have works for me.  My fish tanks range from 150 to 250 gallons. 

[Jim Fisk]

Thanks Jon, I like your change. That's why I like to run ideas by you guys. I do have a boat load of used bird netting and my first attempt way back at first circ. was gravel with no air stones and it went septic fairly quickly and a bear to clean. (I finally dumped it out the back door. I got a little carried away with old fish food as a system starter, yuk)

My clarifier uses Poly Fill with a 12" air stone dropped down the center inlet pipe (particularly important for times I don't have flow thru it) and the entire thing is a breeze to clean as the poly is so light and doesn't soak up any water much like the bird netting) and really needs very little attention but no raw fish waste goes in there and I don't think it could handle it. For algae blooms and sediment after washing gravel it has been amazing. That diaper pail and lid make it look very fancy:-) The filter is fed down the center perf tube which also houses the 12" air stone. I usually don't use the lid but it does look so "high tech"

I don't foresee much solids getting in the outer drum of the new design but I'd much rather find out with bird netting than gravel so I will jump right on your suggestion. Been wondering what to do with all that old bird netting anyhow. I may stick to dropping the air stones down perf tubes so they are easy to remove and check as that has worked great on the clarifier. Now if it would just get above freezing and stop snowing

Jon Parr said:

Jim, that's an interesting bio-filter. I understand that the pea gravel adds surface area and traps solids and floaters for further break-down. I also understand that airstones, especially submerged in gravel, plug quickly and require cleaning, which would be hell to access in a dirty double bucket of gravel, solids, and slime. May I suggest replacing the gravel with bird-netting? It would be quick and easy to pull out, to access airstones and do any maintenance.

[Vlad Jovanovic]

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

Sam Burton said:

I've actually gone primarily to rafts and wicking beds.  I am not very handy and have a terrible time getting auto siphons to work.  It's my on ineptitude.  Raft systems are easy for me because I can make swirl filters easy enough and I add some filter balls in to aid the bio filter.  Also the rafts themselves are excellent biofilters (the walls and undersides of the rafts).  Since I already have 40 or more Earthbox self watering containers, I divert water from the sump when I need to top up the containers.  I don't overdo the stocking density, so I don't really do fruiting plants in the rafts (though I can get awesome growth of tomatoes in the early stages then transplant them into the containers.  Also, I have the solids as fertilizer for the beds and for fruit trees.  I will continue to work on building a flood and drain that actually works.  I don't have the cash flow to buy a kit.  Until then, what I have works for me.  My fish tanks range from 150 to 250 gallons. 

[Jim Fisk]

Sam, I urge you to try my very simple siphon design based on Affnan's work. I have 5 going straight out for at least 7 months now and I have never had a problem. The flow rates have been all over the place so they aren't very sensitive to that and I can't think of anything else that would screw them up or I would try it as I sell quite a few on my Ebay store and don't want to disappoint anyone. For a one to 2 ibc size grow bed filled to 10" (15 - 30 CF) a 1" stem seems to be ideal and that dictates all the other sizes. 2" funnel, 3" bell and 4" gravel guard. Two 90's under the gb with no trap seems to provide all the restriction this design needs. Stem is 7" tall and the funnel brings it to about 9" total. Bell is 12" high (allowing for extension rings in the funnel {2" pipe} to vary water height) and the gravel guard is 14" high and only perforated half way up (chop saw slots in a spiral fashion) That's it. They work. Haven't had any complaints. I use S&D pipe due to high shipping costs but Sched 40 works just the same if you're not shipping them. Also remember S&D (sewer and drain) is cheaper and gives you considerably more flow for your $.

I agree both systems have their +'s and -'s so you need some of each so as not to get bored

And Sam, I would love to see some pics of your swirl filter. I'm a graphic kind of guy.
Sam Burton said:

I've actually gone primarily to rafts and wicking beds.  I am not very handy and have a terrible time getting auto siphons to work.  It's my on ineptitude.  Raft systems are easy for me because I can make swirl filters easy enough and I add some filter balls in to aid the bio filter.  Also the rafts themselves are excellent biofilters (the walls and undersides of the rafts).  Since I already have 40 or more Earthbox self watering containers, I divert water from the sump when I need to top up the containers.  I don't overdo the stocking density, so I don't really do fruiting plants in the rafts (though I can get awesome growth of tomatoes in the early stages then transplant them into the containers.  Also, I have the solids as fertilizer for the beds and for fruit trees.  I will continue to work on building a flood and drain that actually works.  I don't have the cash flow to buy a kit.  Until then, what I have works for me.  My fish tanks range from 150 to 250 gallons.