But, read about this stuff on the planted freshwater aquarium forms. The product is called Safe T Sorb™ Oil Absorbent #7941, it is a kiln fired clay product (remind anyone of hydroton?), and at Tractor Supply Co. the stuff costs $5 for a 40lb bag!
Supposedly, it has to be the #7941, in the green and white bag. Most other absorbents are the last thing you'd want in a media bed because they break down over time. this stuff has been reported to hold up in planted aquariums for more than 2 years running without significant degradation.
Like any media it needs to be rinsed and cycled.
The only negative I can see to the idea so far is that it may be too fine for our application. But you could always layer beds with coarser media on the bottom and use this on top.
At that price, I'm willing to spend $5 to try it out!
I've been buying floor sweep from Pep Boys for many years. I use it in fabric 'Smart Pots' for the plants in my pond stream.
It's heavy enough to use in submerged pots too.
Floor sweep contains silica and is used to absorb oil so that it can be swept up. It kinda looks like kitty litter.
I've been very happy with it.
I use an oil absorber from AutoZone that is 100% diotomaceous earth granules in my seed starting trays. It works great, and is light enough to not damage fine roots during transplanting into the aquaponic system. If I could find it cheaper in bulk, I'd use it in the whole system.
How has the Safe T sorb worked?
I've used the oil absorber from AutoZone for years for plants in those cloth pots around my koi pond. There are two kinds. I get the one with silica. I like the way the water wicks up and it's heavy enough to hold a large plant. I thought about using as an AP media, but it costs too much, and it packs down pretty tight, so I don't think it would work well in a grow bed. Just like pumice it would work in net pots but not as a bed.