Backyard Aquaponics
A place to discuss aquaponics

Has anyone used the slag which is a by product from steel makers and which is also used by cement manufacturers.
Slag from steel makers comes as coarse pebbles and is highly porous. It is cilica left over from production. It is also then used by crushing and put into cement before being sold to consumers.
Has anyone tried this medium for growing bacteria and plants within the aquaponics system?

probably weigh more than Iron ore.....but i haven't heard of it being used. Wonder what could happen to the fish with the additves added to make steel

Yep... it's known as Perlite.... and it's a pain in the a@#e... at least in a flood and drain application...

The slag I refer to defenitly isn't pearlite.
The slag is the same weight as silica i.e. sand.
Basically, when iron is run through the blast furnace the silica is used as a flux and is left over from the process. The slag is the same weight as the orange ceramic balls we buy for aquaculture. The silica is also rock hard and porous. It is basically glass full of tiny air pockets and very light weight.

Perlite is not a trade name but a generic term for naturally occurring siliceous rock.

http://www.perlite.org/product_guides/1 ... erlite.pdf

It has been used in steel making for centuries.... as both a "refractory brick".... and, as you say... a "flux"....

http://www.perlite.org/product_guides/7 ... stries.pdf

Most often the (unexpanded) ore form is used which reacts with slag in the ladle to allow easy removal of the slag layer.

The resultant expanded form used in hydroponics etc... is the expanded form that results from the heating process... and most typically comes from steel making operations...

When uses as a slag flux.... it may contain impurities from the "slag"... and is often used in lightweight concrete production and/or insulation products...

http://www.perlite.org/product_guides/0 ... ncrete.pdf

The pearlite I am familiar with is the tiny commercially stuff available from hardware and gardening outlets.
The slag I refer to is the large rock form which is grey in colour, very porous and somewhat resembles pumice stone.
I presume the material is the same but the size of the product is different.
The slag I am familiar with is about one inch in diameter but irregular in shape.
The pearlite I have bought at commercial outlets is anly about 4 to 5 mm in diameter and will block pipe work drainage.
The slag from iron production is about 25 mm in diameter and once washed doesn't crumble or release any fine mechanical particles.
With this in mind I would imagine there is a potential use for it in aquaponics?
Just some thought for consideration, because the material generally used in aquaponics and aqua culture is really very expensive and imported.
I would like to think that we could find a way to use a local product. The cheaper it is then the more available it is to aquaculture.

If you are using slag I would do it in a trial system first and ask the company who is supplying you with it for full leach test and chemical composition results, they should have them, ask for the environmental officer. When I was working at Mt Lyell, the slag had been used for years as road building and other fill material but due to the liability we had to cease allowing it to be taken off site and used. This was despite the slag being inert and non-leaching.

If you are obtaining the slag from an abandoned or old smelting site, the state environmental regulators should be able to provide you with testing results.

The only slag I have been in contact with (copper and nickel smelting) was like coarse sand and in my mind was to fine to be used as a media in GB's as it would easily form anerobic pockets. I know some slags are more coarse so yours may be suitable.

If it is course and there are leach test results showing it to be harmless and inert I reckon it would be a fantastic use of a otherwise worthless byproduct.

We are talking about pretty much the same material.
It sounds to me like there is some possibility.
A trial would be smart.
Off for a swim in the pool.
Got to keep the body trim.