media for fluidized bed

[mark freshwater]

Hi,
i bought a boyu bed filter , and put some bio pellets in it (

and had a few questions.
I added 20 mg per 100 litre as per instructions, and it barely fills an inch at the bottom of a 1 foot vessel.
Also when i crank it so the media is all turning over the bio media hits the sides of the vessel and is loud and quite annoying but i could get used to it.
i saw a video of a similar one and they had sand in the bottom and then the bio media on top ,
can i run both sand and media , or is this over the top? or could it have adverse affects? ( i got sand with it )
Here is the product with sand in it ( not mine but same model etc).

Thanks mark

 

[mark freshwater]

Edit: or just ditch the media and go rhoaphos ? or both rhoaphos and the bio media.
Sand was free and bio was cheap so doesn't matter if keep it for something else