Backyard Aquaponics
A place to discuss aquaponics

Have been discussing with a roofer the possibility of him making up some growbeds for us out of fibreglass. He was wondering - and so were we -whether the run off would be safe for fish ?
Any comments or advice would be gratefully received!

The plastic growbeds that we have managed to find are quite expensive, and purposebuilt growbeds would be ideal.

If you build some, show us in detail how you did it. I have been wanting to go this route for some time but I haven't the expertise in that field. I am interested in what you decide to do.

Rainwater is being used by several for AP. It does tend to run rather acid in some parts, affecting the ph.

The fiberglass would need to be aged a bit and maybe washed or gel coated.

Hi WD
A lot of concrete ponds are skinned with fibreglass, so it should be safe enough.
Custom built growbeds sounds nice.. you can have all the mod cons

The biggest/cheapest plastic tanks I`ve come across upto now are 400L (86" x 45" x 11") at £79.

Fiberglass needs to be 'aged' or old or, at the most expensive, heated for a few days to get rid of styrene which will leach into the water. The jury is still out wether or not styrene is 'harmful' but it will certainly give most people an allergic reaction and a nasty rash.

I have had a few questions on the subject of cheap tanks, as I have also been looking at cost effective methods. I have an idea where you can get them for free but need to test my theory before I make an absolute idiot of myself!

Hex
We will speak to the roofer who has just done a smashing job of fibre glassing our flat roofs and he said he would fabricate something for us if we gave him dimensions.He would have to make a mold out of plywood but if it came up trumps then we could keep on using it.

Be interested to know where to get those tanks you mentioned as the best sized growbeds we have come across were 6 feet by 2 feet by 1 foot, whatever that is in metric and cost about £130. Ouch.

Bigdon don't worry about making an idiot of yourself I am a past master at it. It makes you more interesting.
WD

If you going fibreglass don't go near any of the styrene based resins or thinners..... there's a particular name for them and alternate resins, but I can't recall it at the moment

Go for marine grade resins and gel coats.... even then there's some concern.... but then again I've heard concerns voiced about polyethylene tanks....

See if you can find someone making fibreglass aquaculture tanks and talk to them about what resins etc to use.

i'm not so sure marine grade stuff is going to be any better, you might find it's treated with stuff to keep anything growing on it while in the water.

I'd find out what they use to make fibre glass eskies.

Don't use GP resin isophthalic resin is what you need.
Then coat using potable coating.

concerns over HDPE? sounds like bullshit to me.

+1

Aup. I found that Garland do gravel trays measuring, 105cm x 55cm x15cm & only cost £12.95 not the biggest or the deepest but more than adequate & cheap enough to have plenty of them , the Garland tray is called Titan, I bought the Giant plus 115cm x 55cm x 7cm, way to shallow, but i,m staring with lettuce so should be ok & that tray only cost £8.50, I'm also looking at producing fidbreglass fish tanks & grow beds, theres a company near where i live sells fibre glass pond kits so cant see the issue with leaching. my problem is that i'm wanting to make the fish tanks free standing measuring 300cm x 100cm x125cm, also wanting to incorporate the airation & pump into the tank.

Hi Schtopp
There isn`t a lot of options over here for growbeds of reasonable size and depth. £79 doesn`t seem to be too bad a price considering it holds 9 bags of hydroton..thats the expensive part at around £14 a bag
I would have thought a fibreglass bed would be more expensive to produce than a moulded plastic one but you never know.

I have made several fish tanks using plywood and coating the inside with fiberglass impregnated with epoxy resin. I am thinking of making growbeds of same material.

Epoxy is much more durable and waterproof than the other resins. But some of the others will work.

my $.02

Agreed!

Think outside the square, literally, with fibreglass. Long thin sides will bow out badly. But long sides made with a polystyrene core won't. Think of making pentagonal, hexagonal or octagonal growbeds. The angles supply a lot of strength. You can make containers from almost anything and cover it in fibreglass. Chipboard covered in fibreglass is a wonderful building material and if you can get offcuts, very cheap. Think of where to put gussets or braces and there's no problems. To get the work done, try bath and spa manufacturers, swimming pool manufacturers and boat-builders. As to what resins to use, the gelcoat/flocoat is the most important. Talk to the resin manufacturers. Their technical sections tend to be very helpful and will often keep a record of unique jobs to show the advantages of fibreglass.

Polystyrene is a good cheap core and glues well with normal woodworking PVA. Laminating it between thin plywood sheets increases the strength dramatically. Leaching is prevented by the outer coats so that is not a problem. Use filler on joints to give a smooth radius and cloth over the filler is also a good idea.