For my current hydrophonics grow it started with 100 seeds on a square meter on the Hydrodensa medium that's discribed in this thread , click this link
hmmm.... Never heard of the stuff... I would have to compare it hand in hand, but I dont think there is any real differance between alot of mediums.
Some people claim lava rock works better then hydroton... I never found that to be the case. Ive used porus rocks from a river bed with good results.. I guess use whatever works!! looks like you got your system down, I wouldnt change a thing.