So excited to discover that Home Depot online carries expanded clay pebbles!! And for one of the best prices around (50L for $33): http://www.homedepot.com/p/Viagrow-50-lt-ViaStone-Hydroponic-Gardening-G...
Also discovered that, for the cheap, HD also covers these larger tubs. And the 50L of clay pebbles fits the tub perfectly: http://www.homedepot.com/p/Plasgad-Large-Mixing-Tub-887102A/202086174
My old growbed was working well, despite being small and very shallow (about 4 inches of grow media), but I knew it was time to upgrade. In the pic you can see that I am using an old Brita fridge filter as a pre-filter for the growbed. I will be moving the Brita off to the side, so it's not in the bed. I learned from my last growbed that some kind of pre-filter is very important (inches of sludge!) Given the low price, I will likely repeat my HD buy and expand my aquaponics setup to include a second bed.
I have six kale plants and a couple swiss chard that I need to transfer to the new bed. I started with just three plants total, and they all grew like weeds!!