Backyard Aquaponics
A place to discuss aquaponics

thanks for your answers length is 10 feet breath 1.2 m and depth is 300mm

As i said before i am willing to just go with expanded clay but as soon as the plants grow to certain height and the wind blows they fall down. Any other media suggestions other than scoria would be appreciated. i can mix them up may be.

Qatada, I have used scoria in my growbeds because a). cheap b). light c). very large surface area d). readily available in Melbourne.
It's bad points are that a). it is quite alkaline and you will have to add HCl fairly regularly for first 12 months to drop the pH below 8. b). it's a bugger to plant into. Ideally you would be better using scoria for most of the GB and then add 60 to 70 mm of expanded clay ball over the top.

buying alkaline rock and adding HCL does not seem good i would rather prefer ph neutral gravel if there is one available in melbourne