I don't know if it is or not. But after you rince it it does not breakdown. As its fired clay. But there are many things you could use such as crush or marbles

I have a good supply of "Hydroton" (my other expensive hobby= orchids), I just don't know if it is reef safe. Is that what you use?

Sweet I have a half dozen orchids. But about 45 house plants.
No I haven't used hydration yet. But it's food grade. So why not

I use small crush and lava rock

I hope there are no heavy metals to leech out.

Derived from a renewable and plentiful source (clay), Hydroton is considered an ecologically sustainable growing medium. The clay is formed into pellets and fired in rotary kilns at 1200°C. This causes the clay to expand, like popcorn, and become porous. Hydroton is manufactured specifically for hydroponic cultivation. It holds water extremely well and transmits it effectively to the plant roots. Hydroton is pH stabilized and releases practically no minerals into the nutrient stream; in other words Hydroton is almost completely inert – except for offering excellent moisture and oxygen capacity to stimulate healthy root development. Hydroton can also be cleaned and reused over and over, so you can help keep your costs down compared to other growing mediums such as soil or rockwool.

Also read artical that stated that hydroton is widely used for biofiltration in ponds and aquariaiums.

Alright just so i am clear they will be better floating with roots exposed to air under the water then planted in a deep sandbed? If this is correct im pulling mine out since i planted then last night

Thats what I did with mine. Make sure you get a spray bottle so you can mist them with fresh water

http://img801.imageshack.us/img801/6302/img2256tm.jpg

http://img845.imageshack.us/img845/6288/img2253uz.jpg

That's exactly what I'm saying. Do a little reading on deep water culture or hydroponics in general. Of coarse most of what you read or see will involve marijuana but the principals are the same. There are lots of tricks to growing plants. Even 24 hours of light is benificial to growing plants in a vegetive state.

And keeping a spray bottle of fresh water is a great idea. Just ensure that you spray plants foliage in early hours of light on as stoma which are like the little mouths on leaves are open in the daylight hours allowing a spray of water to unclog them of salt creep and the fact that water on hot leaves leads to burning

Well here some pictures of mine for now.
http://i1098.photobucket.com/albums/.../IMG_00871.jpg
http://i1098.photobucket.com/albums/.../IMG_00861.jpg
i do use a philips par38 led bulb says 3000K
http://i1098.photobucket.com/albums/.../IMG_00851.jpg

I use crush rock for mine.