I like deep grow beds generally. See remember it isn't just how much depth you need for the plants but you also need depth for filtration. Now for growing small things or for a small system on an extreme budget, the mortar tubs with some bracing can work and they are between 6-9 inches deep usually depending on model. These are at risk of clogging if you are growing lots of big tomatoes though.
Then the more "standard" 12 inch grow bed depth is definitely good. If you can't afford to fill the whole thing with clay balls you might look into using some appropriate type of gravel in the bottom layers so you don't have to spend as much on the expensive clay. The heavier gravel will give more support to big plants too.
Now I've been known to simply cut IBC's in half as grow beds to make each half about 18 inches deep and that is a nice grow bed.
Or, most of my grow beds are actually 24 inch deep 100 gallon rubbermaid stock tanks.
Now almost any size/depth grow bed can become root clogged depending on the plant growing and how long it is left in to fill the bed. Smaller beds/buckets are at risk of root clogging from tomatoes. I've had the large beds clog with roots from Bananas or Lufa vines. Beware any aggressive perennial like mint or watercress, mint will clog most any bed it is allowed to go rampant in so I would say contain it in it's own small beds that you can dump and re-plant as needed since if you plant it in a huge bed it will be too difficult to dump and re-plant after the mint takes over.
bill... did you use some of the growstone? I wonder if it really is more economical than the Hydroton beads. From what we read that it is a step down in use from the hydroton beads and above the lava rock (meaning in using it with your hands). Comments anyone? Mary
Bill Moore said:
Mary.... the bottom 1/3 is lava stone, top 2/3 is hydroton. It's deep enough that I don't have to reach down into the lava stone. I have not yet tried growstone. May try when I expand my grow bed after I build my greenhouse.
Coty, first off, I'm not an expert; I'm just starting myself. Are you using a sump tank or an indexing valve to distribute the water?
I'm using a 100 gal Rubbermaid fish tank and 50 gal sump set up in a CHOP2 configuration. I have two 50 gal Rubbermaid media beds, about 10 inches deep and a 2 by 4 foot by 6 inch deep DWC (float) bed. Float bed stays full of water and is constantly over-filled and drained with nutrient. Media beds have bell siphons for fill and drain. Without lowering the level of the fish tank(using a second pump) I can't fill the two media beds at the same time. I don't have enough water in the sump tank. I think you may run into the same situation.
Regarding depth of the float beds, for leafy plants that don't grow too high I believe you'll be fine. For the media beds, leaving some water in the bottom and keeping an inch or two at the top dry doesn't leave a lot of space for any plants that need a larger root ball. Just my opinion.