Backyard Aquaponics
A place to discuss aquaponics

what size are the bits of gravel?

8-10mm mostly

Get the screened gravel. Cheaper, better on hands, and lighter. Wins on all counts.

It might pay to wash it then spread it out in the sun for a day or two to get bleached and dried in this manner. Just in case it's been damp in patches the whole time and there are eggs and critters unseen.

Hi jaymie i cleaned 1/2 metre scoria today in 15 minutes [try to park front of ute on a hill or something water runs out better and carries dust with it] its easy

I'll be enploying the same method with box trailer instead of ute. Good idea. My choices of gravels will be 10mm drainage gravel (the grey looking angular stuff) or a rounder 10mm type called ulluru. The problem I see with the second type is that once the dirt and stuff is washed off the gravel (it is coverred in the stuff) I expect the gravel to be quite smooth in texture (not quite polished, but somewhere towards that). Does this make that one less suitable. In most other respects this would be the one I would choose because of its round shape. Having said that the drainage gravel is what I have been using in my little test bed and it seems to have worked fine. It would also have less crap to wash off it.

Can you define drainage gravel a bit more VB? Scoria?

TO me it looks almost identical to the crushed rock used in concrete mix

Here is what is sold as 10mm drainage gravel. I think it is probably crushed granite. It is not round. Is more flat and therefore would be likely to house less oxygen between the rocks when put in the grow-bed. Should be okay though I reckon - what do you all think.

AA - wish it was scoria. In Qld scoria is very expensive as it is shipped up from down south. Only found 1 place that sells by cubic metre and it was something like $300 a cubic metre and a bit of that would be dust. In the bags (which is how it is normally sold) it is not much cheaper than hydroton.

Looks pretty sharp VB. I'm going to get some of the bean gravel Daniel spoke of (Where did you get it from Daniel?) easier on the fingers, for the top 10 cm's and have coarse stuff underneath to better house the bacteria

Gravel the size of an echidna! It looks porous VB, what do you think? Porous is good.

Monya, on layering, I tried. It all gets mixed in soon as you begin pulling root systems out, not much you can do to stop it.

I'm not so concerned about the fingers. Can always use some sort of implement. I am more concerned as to whether this gravel will have sufficient spaces between for air, roots etc and not clog too badly. Eventhough it is 10mm in length, the width is less because of its shape. The ulluru gravel may be better, but it is twice the price and the surface area of each piece is coverred in a layer of dirt, which is what I think gives it its red colour (and then is called ulluru). I don't think we get, in Qld, the pea gravel that the westerners use. I may have to look at some more lanscape joints before making my final decision - or I may just go with the drainage stuff for my first big bed and see how I go. If I have to replace it it is no big deal (it is cheapish and can be used in other applications at my place, like drainage, if I need to swap it over).

I'm just soft! So layering is okay until you actually use the beds!

What do you mean by 'layering is okay until you use the beds' stu?

All I meant was, it's fine to have layers with the smooth finger friendly gravel on top, but as AA said, as soon as you start harvesting, it all gets mixed up anyway, so you might as well go for the gravel that's best for the system, ie, plenty of airation and surface area, rather than one that's kind on my softy fingers.

Stu, it was from Garden Grove, and it was $85 a tonne (i think i said $65 in another topic). It is abit on the big side, compared to what most others are using. But i wanted something smooth, and it was the best i could find. (im happy with it though)

Oh and they had azolla there too, well i think it was azolla anyways. I got a "couple of handfulls" for $2.20