Backyard Aquaponics
A place to discuss aquaponics

I only need enough 20mm blue metal to fill 1 bathtub. Does anyone in Perth SOR to Gosnells have extra they don't need?

or failing that , anyone interested in sharing a trailerload?

http://www.allearth.com.au/go/for-your- ... -materials

Does it have to be blue metal?

I have about 600L of 20mm pea gravel -- exceptionally clean (it was washed on Saturday). I'm in Leeming.

Send me a PM if you're interested.



Scott

bunson,

is pea gravel ph-neutral in WA? always not been sure of getting it, is it as dense as blue metal?

ta.

doesn't have to be blue metal, just that my other 3 beds have it.
pm sent

Blue metal for free... http://perth.gumtree.com.au/c-Stuff-for ... Z356887388

wonder how many AP addicts will be shoveling tonite?

When the system was running, I used to have the gravel, hydroton and crushed shells in the GB... pH stayed constant for the entire run; 'measured' through observation that the shells didn't dissolve (so not acidic) and any alkaline-hating plants also thrived (so not alkaline), so I guess pH was pretty much neutral. I rarely did any water tests or any tinkering with the system once it was finally up and running.

You can see the system as it was back then did ok for itself.


As for density, gravel is hard and heavy; great for holding plants securely in place in even the strongest gales, but its much harder to work with than the much lighter-weight expanded clay (but not impossible).


Scott

Thanks Scott for your reply .

The pea gravel seem to me to have a little more porosity and hopefully more surface area for good bacteria than the blue metal, so am glad it's ok to use in WA.

And yes, was considering just putting the more expensive expanded clay only on the top 100mm or so to make it easier to work with.

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Unfortunately, the clay doesn't stay on top for long, it tends to mix quite quickly as you harvest plants, especially yanking out big rooted plants like laksa mint, tomatoes and even one curious variety of garlic chive which went nuts in the system but each plant had a root ball the size of a softball. If you're going to plant long-lasting trees/shrubs/etc then the clay wont get mixed too quickly; but then again, you don't need kind-on-the-hands clay if you're not going to be working too much! Sort of a double-edged sword.

Good luck with your adventures anyway.


Scott

I guess I should explain why I am getting rid of the gravel and going 100% clay:

Recently, I came into some small $; SWMBO and I decided we'd use those funds (which means she decided) to do whatever we could to make our lives just that little bit easier. Shovelling out the mix and float separating the clay from the gravel was an arduous task but I am satisfied with the result; the choice to do so was not based on the performance of the pea-gravel but rather the simple fact that clay is easier to work with, although WAAAAY more expensive than gravel.

Each will have to do their own cost-benefit analysis; in my case, when I started I was on a very strict budget so went with a majority of gravel, but now that budgetary constraint has slightly loosened, so I can 'upgrade'.



Scott

OK maybe I should plan for 200mm of expanded clay, and only 100mm of the heavier to work with stuff at the bottom

I never tried it myself, but, depending on the root depths of the plants you intend using, you could position a piece of shade cloth or weed mat between the gravel and the clay? Of course, this will limit you to shallow rooted plants, or you could have a 'deep end' and 'shallow end'?



Scott

Scott,

sounds like a plan. i think what you said on 'depending upon the root depths' of the plants people intend to use, that's the real basis for making any determination on depth.

Deep rooting plants would likely end up going all the way down to the bottom of the GB, which would nullify the point of making it easier to work with, as you said, you pull the whole lot out, including the gravel at the bottom, and end up mixing it with the lighter stuff.

Weed mat perhaps to separate the two mediums, but then not sure if the solids filtration would work well with such a barrier in place.. I was expecting all the 'solids' *using the GB to break down solids* to filter to the bottom of the GB and get broken down there over time.

Maybe I'm wrong in that thinking, maybe it's better to have the solids nearer to the surface where more aerobic/bacterial action would be working?

Gutter guard instead of weed mat?