Im gathering things to start a ebb and flood system.

Does it matter what expanded clay i get?

Can the type of expanded clay you find in the supermarket be used. or does it have to be specifically for hydroponics? the supermarket stuff is cheaper.

Yeah you can use the supermarket stuff but make sure you wash it really good. One thing that can create a problem is that they might contain alot of limestone and that will rise the ph. The special hydroponic clay are ph stabilised to ph 7.

Thanks
I will try to find the hydroponics clay then. sounds like its easier to work with.