Aquaponic Gardening

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I've been working on a new aquaponic system and recently developed concerns regarding the seasonal swelling/shrinking of wood due to moisture and temperature changes.  The entire system will be indoors, but the grow bed is made out of plywood and 2x4s.  To waterproof the system, FRP wall boards were purchased and the system was sealed with 'farm safe' caulk.  Additionally, the FRP boards are held onto the wood using an adhesive caulk.

I fear that movement of the wood could cause the caulk seal to break if the FRP shifts.  Has anyone had experience with wooden grow beds?  I looked into pond liners but they are very expensive and sometimes leach chemicals into the water.

Pictures are included below. Any suggestions would be appreciated! :)

Caulking Close-Up

Grow Bed & Fish Tank

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go with Duraskrim.. for a box that small it would cost about $40

From what I understand plywood does not expand and contract like a 2x4 does. But I agree with rob, get yourself some duraskrim and make your grow bed last much longer without leaks.

Thanks for your responses! It seems that plywood and 2x4s in the long direction exhibit negligible expansion, but I'll definitely order some duraskrim material for the long term.

As stated, tts not expansion and contraction that is of concern, but the flexure of the wooden members from the loading, especially variable loading from flood and drain.

I've never heard of "farm safe" caulk. Do you know if it's potable water safe?

Hi Jeremiah,

The caulk is listed as non-toxic, livestock safe, carcinogen free, and meets California's prop 65.  I trust it, and assume that it's not NSF listed for potable water because that process is expensive.

If you're interested, the company can be contacted at <>.  Let me know if you find out any additional information!

Here's the amazon link to the product: 

That looks like great stuff!  Thanks for the link.

If you're ever looking for NSF potable water paint you can find it here.  Expensive is right, though.

the calk would be about 1/3 of the cost DuraSkrim liner.. i recommend putting your money toward the right purchase and be done with it...   heck.. i have that much liner laying around... im willing to send it to you for free, just to see it done correctly.

let me know if your interested.

Rob - thank you for your generous response! I have already installed the system with gravel, FRP board, and caulk, but would be interested in the duraskrim for when the caulk starts to leak.  If you can provide dimensions, I'd be happy to pay for it through ebay.

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