I'm looking into setting up an aquaponics system, which requires me to acquire a large tub (on the order of 250L, relatively flat) to use as a grow bed for the veggies. Does anyone know where I could look to find a source of such tubs? Perhaps disused from some other purpose? All those I've seen commercially seem exorbitantly expensive for what they offer.
In addition, I've read something about "food grade" materials (usually regarding plastic) for this use. If the containers are not designed for growing good, how can I determine whether the material is suitable?