Backyard Aquaponics
A place to discuss aquaponics

Thanks again Hex, I did not realise that the pump might not cope with the solids. I'll try to find more information on that.


I don't get that bit though; do you mean for the growbeds, the sump or the pond?


Yes, I meant treated wood, I don't know how it's treated though (edit: you're right, it's treated with copper, chromium and arsenic). The wood won't be in direct contact with the water (as the pond, growbeds and tank are lined). However, rain might be a problem, as the growbeds are right above the pond; do you think this will contaminate the system?
Thanks for pointing that out, you might've saved our lives!


And stupid me, I don't need a one way valve to keep the 180L tank from draining when the pump's off; I just need to put the outlet above the water line..

CCA is really bad shit Thomas. If you are intent on using it at all, be sure there is 0% risk of any water coming into contact with it then enterring the system.

Alright, no treated wood then.

The only two alternatives I can think of are hardwood, and untreated planks. As untreated planks won't survive the weather, they'd have to be painted, which I think is also toxic, so that probably rules that out as well. So I think I'd have to go with hardwood.

Thomas,
Hex and F&F are joking about how every container that could possibly be used for a grow bed or fish tank is turned into one as soon as the legitimate owner's back is turned. In this case some small children quickly losing the use of their sandpit as it is turned into a grow bed. Filling the sandpit with gravel would just enable them to cut out a step in the thieving process

I dont really have the knowledge but iam sure that there is ways of painting with organic paints or non toxic paints if you look around a bit in stores you might find it... ryan

Here we can get woods like locust, cedar or redwood that are naturally rot-resistant. You might even be able to seal them with oil -- like cooking oil, or something made to finish children's wooden toys. If it is safe enough for the baby to chew on, it shouldn't harm the fish.

I've been searching some Dutch Koi forums and I've found that many people have used simple wood stain (is that what you mean with 'sealing oil'?) for the wood at their ponds. It seems that wood stain, after drying up, doesn't affect the water at all.

Now I come to think of it, I once made a small container for growing herbs in; I used the cheapest wood available and some sort of wood stain, and after at least 4 years outside in the rain it still looks like new, and I love the dark colour. So I think I'll just use cheap wood, and stain it.


Thanks for all the advice, you've all been very helpful!

Xzorby, i remembered this while looking up stuff of vegetable oils as a fuel................



Try and find the oils mentioned above rather than a stain, as its often the unlisted ingredients that can be the most detrimental for fish

I only managed to find linseed oil (apart from some very expensive finishing oil which I won't buy as I'd be better off buying hardwood). I also found that treating with linseed oil does not protect against UV, it doesn't harden and all natural oils are food for mildew..

Furthermore, pure linseed oil takes weeks to dry, and you need about three layers of it. There are 'boiled linseed oil' and linseed-based products on the market, which dry within a day and are usually mildew resistant, but they contain metals (I've read arsenic, beryllium, chromium, cadmium, nickel and lead); boiled linseed isn't actually boiled.

So I'd have to use pure linseed oil and find a way to dry it quicker (I've read about people using an iron, or maybe I could use a blowdryer after applying the oil?), and find a way to counter the mildew.

25 square meters of wood seems quite a lot to 'oil', by the way, also because I'd probably have to sand between layers of oil (or any other finish, for that matter) as well.

That said, linseed oil gives a beautiful stain.. Any ideas on how to dry it faster, and how to counter the mildew (some sort of natural or non-toxic varnish?)

i think the "drying" is actually the oxidation of the oil. I'm fairly sure that its linseed oil that can casue discarded rags to sponaneously ignight, burning down peoples houses. and yes, i have ssen a tme lapse video of this

The oxidation reaction was the one that i was talking about im my previous post.

Anyway, its a chemical reaction, so the application of heat will speed it, but id probably try and elevate the ambient rather than apply direct heat via a heat gun. got a sun room?

Yer on it steve with that first blerb you cut n pasted. Looking for fuel eh!!.
Thomas there are similar plant based stain/sealants that are in the market place as we speak.
PM me if you would like some more info.

what about marine grade plywood? or is there something in the ply process that is not food friendly?

I'm afraid we don't have a sunroom.

I've read about people getting good results with applying lineoil and "burning it in" with an old iron. I know it's dangerous, but I'd be doing it outside, and of course I'd be very careful.

I've read that sulfur and baking soda can be used on plants against mildew. I might try mixing it with the linseed oil to try and make the wood less susceptible to mildew, but I have no idea if this will work.

Jaymie, marine grade plywood (WBP; weather and boil proof) is not an option, as it's almost as expensive as hardwood here, it only comes in sheets, and it still requires some sort of finishing. I think I'd be better off buying used hardwood planks.

I think I'm going to try using raw linseed oil on some wood scraps I have lying around and see how it works. If it doesn't, I'll just have to buy hardwood (as commercial plant-based stains/sealants would probably be quite expensive, closing the cost gap between cheap wood and hardwood).

Update! I've changed the design quite a bit, I'll just make a big rectangular pond (300x120 by 85cm deep - 2200L) with a rectangular GB over it (300x90 by 30cm deep - 800L). The wood on the top of the pond will be mostly resting on those 60x40x6cm tiles, the growbed will be supported by four 9x9cm beams going into the ground (two in front, and the two from the fence in the back).
I'll use a small pump, constantly on, and an autosiphon.

(Click for sketchup file)

I got a really good deal on some new hardwood planks, and a big 'concrete plywood' plate (will be made into bottom of GB), so no fuss with linseed oil and such.

The hardwood planks (you can also see the end of our small garden):

The cat inspecting the planks (also in the previous picture):

The coated plywood, standing where the system will be:



Also removed the tiles where the system will be; it was paved. Those 60x40x6cm tiles are bloody heavy! I might just put them back at 65cm into the ground, would make a nice bottom for the pondliner to rest on, and would save the fuss of getting rid of them. Dug a small hole to see what the soil is like. Trying to find somewhere to dump 2,5 cubic meters of soil at the moment, so I can start digging (very small garden, so no machines..)

Going to get pondliner, a small pump, air pump and water test thingies (should I buy those strips, or testfluid?) tomorrow.

Furthermore, dad agreed he might fund the 150 euros needed for 800 liters of hydroton!

I was hoping you would use fish oil to seal the wood, that would have been ironic!