Commercial Growbed Construction

[Mary Hundley]

I am looking to construct 12 - 60 foot growbeds...2 feet wide and 14 inches deep.  My intial concept was to use 24' water pipe cut in half (schedule 40), until I found out the cost....about $40 a linear foot.  Second idea was to use black culvert pipe, again cost is an issue.  I've tried contacting a firm in New Orleans that produces shallow fish raceways that could be adapted as growbeds, but to no avail.  I am concerned about doing a plywood/pond liner construction due to durability issues over the next few years.  Am looking for suggestions and appreciate the advice.  Thanks, Mary

[Izzy]

Treated lumber used to contain arsenic. I have no idea why this would be a problem now.

[Izzy]

You really want to stay away from spending a ton of money on your start-up cost.  That's the fastest way to go out of business.

 

White PolyMax HDPE costs 1600% more for the same 1/16" (6 mil) size of PE sold at Lowes/Home Depot.  To put it in perspective a 100' x 20' 6 mil black or white PE roll costs about $99 whereas the same amount of material would cost you $1563... In other words, you should just buy 45mil EPDM Pond Liner (fish and food safe and naturally UV and tear resistant) with a LIFETIME warranty for the same price or LESS and this liner would be almost 8 times thicker...

 

Heck, get 3 orders of these and you can get liner for all 12 for $600... this stuff is 20 mil versus the 6 mil stuff.

20 Mil 20 x 60' Vinyl Tarp 16 oz ReUsed Billboard Cover

 

The pipe you mentioned is cheaper than all of the HDPE they sell per square foot of grow space (everything except the 1/16" TC mentioned of course)... I have used 20 mil pond liner and it can handle the weight of the gravel.  EPDM rubber liner would of course last a heck of a lot longer and stand up to the gravel. I am not sure if the 6 mil HDPE can handle 14" of gravel, but maybe someone has tried it?  If it wasn't for the gravel you could try the 6 mil PE liner from Lowes/HD that costs $0.05 per square foot.

[TCLynx]

The thing not figured in this pricing is that all the pond liners are going to need a complete box constructed to support it and the gravel.

 

As far as using pond liner, I know the EPDM stands up well against gravel wear and tear, but the moist space between the gravel and a wood box is very attractive to termites.  I still use EPDM but I will no longer endorse it's used against wood in termite territory.  I don't know if any of the other pond liners are any better proof against chewing insects that are going to love the most space between them and wood.  (The space between any liner and a wood box is going to have condensation in a humid climate since when the grow beds flood the plastic will be cool.)

 

There are several liners that are sturdy enough to support water with a radius on the ground without ripping out of the edging on the frame but I'm not sure if any of them will handle doing that with gravel.  The HDPE plastic is sturdy enough to do such a thing with the bottom supported on the ground.  Any type of liner to do up at table height though is going to need the bottom supported so suddenly this becomes a pretty costly method in terms of needing nursery benches or something to support the bottom of the liner as well as a frame to support the top edge if it's HDPE plastic or complete sides (that won't bow out) if using a lighter weight pond liner.

 

I think this is a bit portion of why few commercial operations use large scale media beds.

 

Have you looked into masonry grow beds?  Ferrocement or block or brick?

[chris taylor Swamp Creek Farms]

He said he built his greenhouse and frames with treated lumber, and at the last minute the state denied him,  because of the treated lumber.  It is a tilapia farm that has been running for years, they wanted to do AP,  did alot of work and got denied to sell organic.  He was real bitter when I talked with him.

Ryan said:

That doesn't make any sense if he was using a food grade liner.

chris taylor Swamp Creek Farms said:

a guy in georgia could not get certified for organic because his frames were built with treated lumber,  check it out before you build

[TCLynx]

Ah, I see if the green house over the grow beds were with treated lumber then condensation dripping down into the system could drip off the treated lumber, that is probably what got him.  That sucks.

[matthew ferrell]

We are using concrete blocks stacked two high with liners in high tunnels.  We used a crushed rock on the floor, but I am sure sand would work as well.  Liners are about 250 bucks each at 45' lengths.  USDA is matching on high tunnels as far as I know, but require everything to be on ground level.  If you go this route, we have both plywood and block raceways and I would highly suggest the block.  It is much easier to work with.

 

[matthew ferrell]

What feed was he using for his tilipia.  I was under the impression any fish fed any feed with fish meal or oil in it was an automatic denial of organic certification.  Is there any aquaponic farm in the US that is certified organic?

[TCLynx]

There is no organic certification for fish!  It doesn't exist, at least not yet.  You might be able to market fish as "naturally grown" or "Sustainably grown" or something similar but there currently are no certified organic standards figured out for fish.

 

There are aquaponics farms that have gotten their plant produce certified organic.  Friendlies in HI was the first and they have had several farms attend their work shops and follow their methods and get certification as well.  The Organic certification is only for the veggies, NOT the fish.

[Averan]

I can tell you that the used billboard vinyl pvc tarps are super durable and pretty darn affordable: https://billboardtarps.myshopify.com/collections/tarps

They can custom make extra large sizes if needed.

 

I have 2 custom hanging planter troughs filled with gravel and water suspended only by 2x4 framing along the top (no sides or bottom) and have no trouble at all!  This stuff is 3-ply and flexible.

[TCLynx]

I've got mixed reviews on the billboard tarps.  I know some people who have done great with them, I also know that it is a sort of take your chances as to if it will be good or not.  I mean can you really complain if you got the tarp for free?

But anyway, the one I got leaked and I know others who have gotten the billboard liners that had holes.  But then Cosmo has one that has been working to line his two raft beds just fine and Michelle has been using them for her raft beds.

 

I think the condition will vary greatly from billboard to billboard.  Mine felt a bit brittle to me and must have been up in the harsh Florida sun longer than some others.  Then again, I'm used to handling EPDM liner which is very pliable and definitely durable even when you slip with a knife sometimes.

[Averan]

they certainly feel more 'brittle' than epdm rubber-like liners....more like a super thick plastic tarp with a layer of nylon thread in the middle.  it cuts pretty easily, very easily, but resists tearing extremely well.

you make a great point about the crap shoot when purchasing and the possibility of tiny holes!  i didn't think about that.  it would be impractical to inspect 100' of tarp for holes, let alone actually seal them all.  darn.  and it was such an affordable solution!

[TCLynx]

Depending on the situation and use, it might still be reasonable, but yes a bit of a "crap shoot" as you say.

 

If it's tough enough for hanging leaving most of it accessible from the outside, well perhaps one could deal with leaks then.  Mark them when the bed is full of water and leaking and then come back and patch when it's drained and dry enough.