Ok heres the verdict.
Black Onyx Sand (code name MUD). It says its great for plants, and i guess so what would be better for a plant to grow in MUD or sand? id guess mud cuz thats what black onyx sand should really be named.
Tahitian moon sand, hey its actualy sand not sand mixed with mud. After washing it for a hour and putting it in the tank slowly its CLEAR and the stuff SINKS not floats, i even dropped it from the top of the tank to test near the filter and the filter didnt even suck it in, the stuff went straight down.
My official recommendation, go for Tahitian moon sand, i bet it even siphons better too.