My 2 cents
Maybe some of the live sand from your primary tank 1/2 in or so, and a piece of live rock.
I am starting to think the best bio filter is lots of sand and live rock, every thing else is just water clearing .
I cycled a small tank with a sump using weekly additions of live sand from another tank for about a month some brisstle worms for the sand it cycled really fast.
The only problem was a sudden PH drop, the buffer is used up proably by the bacteria cycling the stuff out of the water.