Backyard Aquaponics
A place to discuss aquaponics

wow you folk here in the forum are efficient. I ask in intro if red scoria ok and it was posted already maybe i shoulda looked harder first?

Thanks Steve,
Have been s-l-o-w-l-y installing AP system using red scoria. You've put my mind at rest. Moved house twice but now settling sys in - hot house soon plus fish.
Ta.

So does anyone use plain old blue metal screenings?
Or is scoria lighter and rougher and so gives a better surface area? and perhaps better trace elements. And from experience with scoria,it may (ever so slightly) break down and release some of the trace elements in it, whereas you'd have to wait a fair while to see blue metal gravel break down in water!
Does anyone know where to get black Scoria in melbourne? I've only ever seen red..

yes Blue metal is used by a number or members. Be aware it's very dense so you growbeds will be quite heavy. This means your stands may need to be a little tougher.
Blue metal is discussed here by les and others who use it...
Probably discussed in many other places as well

In my system i have an experemental bed 4 divisions 1vemiculite 1 scoria 1 hydrotron 1 blue metal they all get the same amount and time of water they drain the same and as you will see when you visit they all are growing the same

Is scoria the same a lava rock?
T.

Basically... yes

stuff they use on tennis courts... (but ours is coarser )

There is an article in issue 3 of the magazine that relates to blue metal "Trial by Media" if you are still interested.
http://www.backyardaquaponics.com/magazine.html

I was asking because I would think, theoretically that it would have positive effects. It has a lot of surface area for the bacteria and its light. However the sharpness can be an issue also. I have opted to make it a bottom layer in my grow bins. The obvious problem- as you old timers will know -is that if you ever have to change or work on the medium you mix the layers together! VERY frustrating. I have thought of placing a perferated solid material (blue foam maybe) between the layers to assist in this. Anyway, thanks for the info, I'll keep reading.
Tony

Scoria is volcanic rock that has been rapidly erupted from a volcano. That is what gives it lotsof little air holes in it and makes it light. Near Melbourne it is a red colour cause its rich in iron hence the rust colour of the water. To make scoria into pebble sizes it is crushed hence the rough edges. these should smooth a litlle bit over time but very slowly due to rusting. The chemical composition of scoria will depend on the chemical composition of the lava that it originated from therefore one analysis of scoria wont be the same as the next one. It should not contain any more heavy metals than most other rocks and any way the slow rate at which any metals would leach into water should not cause any problems.

I was thinking about using scoria and have no concerns about its chemical make up, however as I was going to construct my growbeds on the ground and lined with pool liner and given your thoughts about its roughness it may limit the life of the liner.
Any thoughts on whether the roughness of scoria would prick the liner?
Off topic: Are pond liners safe for use in aquapnics?

I would have no worries using the thick EPDM pond liner with the rough and sharp rock. I have been using the firestone pondguard liner which is safe for fish.

Anything thinner you will have to make your own decision.

Thanks

If lava rock (scoria) is so high in iron couldn't it be used, at least in conjunction with other media to aleviate iron issues from plant development, therefor no need for chelated iron? Just asking.

T.