Comment

Comment by Bob Campbell on March 6, 2013 at 10:27am

@John - Here's a quick drawing of what I'm talking about.  I think you and I are on the same page, but I like graphics.   I'm sure backer board would work, but plywood is stronger, lighter, and maybe cheaper. 

I know that backer board will eventually dissolve if left submerged - I know it's not going to be submerged but I thought I would tell you of my experience.

A gallon of resin costs about $40.00 and would be enough to coat about 200 sq ft of plywood.  I get plywood seconds for half price. ask your local lumber yard.

Comment by Matt Miskinnis on March 6, 2013 at 9:47am

Hi, Sherri, I can't wait to meet you!  Jim and I are figuring out the semantics of when and what time to come out, I can't wait to see the fishy's!  My grow bed is 16 square feet and from what I've been reading I would want to have one fish per square foot (I hope that's correct from what I remember).  I'm already planing on adding more grow space, but I'll do this in baby steps and try not to get a head of myself 

Comment by David Schwinghamer on March 6, 2013 at 9:28am

You guys might want to try the 1" pink board from owens corning, its been working great for me.

Comment by John Malone on March 6, 2013 at 8:29am

Hello Bob,

It looks I am heading down the same path as you with regard to DWC.

I'm considering using cement sheet backer board as the platform over the water in which to put the plant pots. It's relatively cheap, inert, waterproof and should last a good time.

I checked out the FRP sheets in the hardware store and they look good, but are pricey, as you mentioned.

I'd value your input.

Comment by Bob Campbell on March 6, 2013 at 8:14am

This is my PVC/FRP DWC bed.

I have 2" foam rafts and a PVC/FRP pontoon raft.  The foam gets a little water logged after a while. I prefer the pontoons with FRP (Fiberglass Reenforced Plastic).  They are easy to clean and remain buoyant, but they are expensive. 

Next time I will build solid plywood platforms over the DWC tank. Plywood will last many years and if coated with fiberglass resin I expect they will last a lifetime, and be very easy to keep clean.   Rafts do well with an air space between the platform and the water, but this space should not be exposed to light or ventilation which can cause the roots to dry.  Keep unused holes filled.

Comment by Robert Rowe on March 6, 2013 at 7:50am

@Sheri

The biggest is up to over 4" the plecy is 18"

Comment by Sheri Schmeckpeper on March 6, 2013 at 7:19am

OK, we have good fish. :) 

We just switched from 1" to 2" for the reason Jim mentioned. It does come at a cost, though.

I love to see the strength test! Rhiba Farms had problems with the scored boards breaking so they switched to unscored. We got the scored (it's all we could find, and that was hard enough), but were concerned about the strength...not so much after seeing this brick test!

Comment by Jim Troyer on March 6, 2013 at 3:07am

Hi Doc:

The 1" blue board allowed the root ball and stem to sink into the water column as the tray got too heavy from plant growth.

I have been reading in the raft group that they are noticing greater health and growth rates when the first inch or two of roots are held above the water to allow O2 uptake without having to add air into the the raft tank.  They are building PVC pontoon style grow trays instead of using blue board.

I'm intrigued with the success with your new project.  How about a tour?

Jim

Comment by Dr. George B. Brooks, Jr. on March 6, 2013 at 2:57am

@Jim. Interesting. What do you mean "out of the water?"

Comment by Jim Troyer on March 5, 2013 at 11:57pm

regarding the 1" blue board below:

I used 1" the first time and the flotation is not enough to keep the plants out of the water.  Double up your sheets for 2"  or add pool noodles or something similar to lift the plants out of the water after they get going...

The positive comments regarding keeping the root source out of the water for O2 uptake should be considered when making your rafts...

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