Backyard Aquaponics
A place to discuss aquaponics

Hi Medz,

I'm just about to knock up a growbed stand and wondered what the dimensions are (thickness) for the main bearers under your growbed stand? Also what wood did you use? I want to try and avoid treated in case there are any problems with toxicity.

Cheers
Matt

Anyone else? - Notice its been a while since Medz logged on.

Untreated wood arround water won't last long unless its expensive hardwood

Yeah - Was thinking Jarrah, just not sure what dimensions necessary to ensure it does not bend under the weight of the GB. Might be cheaper to buy angle and weld!

Wood is actually pretty strong. Check out this flimsy pine I used under the GB on my old IBC set up. There would have been approx 500kg bearing down on those but they started to bow after 3 months or so as they were often damp. I wouldnt recommend it but gives you an idea of the strength.

Yeah Thanks Charlie - I'm coming round to thinking some angle and a welder is better. I'm not sure what size wood is necessary to prevent long term warping around water - and these would be 2m spans of wood.

Matt,

By the looks of it the wood used is Pine Fence posts, 125x75. They look to be treated as they are designed for in ground contact, my guess is CCA, but not sure if other suppliers use different treatments. Cheap, and readily available in Perth.

Typically Fence posts are only roughly graded, maybe chuck out if a really bad knot, often cut from the Heart, which doesn't treat as well as the sapwood, and is not as strong. My preference would have been to have the boards on their skinny edge, as it is stronger that way.

Myself, I have 2 x 90 x 90 posts treated to H4, (were meant to be used as stumps for houses, but the drying went a bit wrong. Whilst still perfectly good, we chose not to sell this batch to the public). Okay for the span of an IBC, would go for three if using one of those grow beds.

Thanks DB - Do you have any info on the risks of the wood treatment leaching out during rain etc and causing toxicity for the fish?

Dr bee, I thought CCA treatment had been phased out in WA and replaced by other potentially less harmful timber treatments such as ACQ, CA and LOSP. Can you enlighten us?

Hi Medz,
Are you testing the water? and how long did it take to cycle the system?

Just curious, I've just semi-planted out my first IBC system and I'm debating whether its safe enough to put fish in yet!

Hello Bunyip! How about you start a thread in the Members' Systems area and give us some details about your IBC system and what you are up to? That way you will be sure to get lots of advice re cycle times and when to introduce fish.

mattyoga The masters at North lake rd have 3m lengths of Jarrah 5 by 1 and half for about for abou $30 bucks each they would make good grow bed bases.

CCA is still going strong. It is the cheapest H3 termite protection available for houses and roof frames.

I believe it is best for in ground contact H4 and H5 protection levels (ACQ suppliers would probably challange that thought). CCA is banned from playgrounds and handrails, as kids will put their hands in their mouths, although personally I don't believe the levels of C, C or A that is ingested will harm the little guys. Environmentally, its better rthan LOSP as it doesn't flash off into the atmostphere, the other treatment processes , I am less familiar with.

I have looked at it before and there is risk of leaching in contact with water. How much - very little. I wouln't put my posts directly in the water, but for the little bit of splash that happens, I am not concerned that I am getting a build up of nasties in my system. I don't use timber in my GB, but I would use it around a soil based GB.

The way I see it, any of the wood that is exposed to rain is outside the line of the tank anyway, so run off intothe tank is going to be minimal. So you give it a lick of paint and you will be covering the treatment anyway.

If you have a gal painted stand, how much zinc come off in the rain?? If you have Hardwood, how much extractives come off??

Hope that helps.

Thanks DB and TP - thats been useful.