33 hex with two 303 canister what to put in for media?

[damtrees420]

just trying to start a seahorse tank i bought two 303 canister the older gray ones and just wonderin if i will need both couldnt hurt right depending on how much flow will be in the tank ? as well i am wondering what kind of stuff to put in the chambers not to sure how to run it with out a sump as far as what media i can put in them thanks again ther will be about 30 pounds or so of lr in the tank as well