I guess it depends on how close your tank is to the wall if its really close to the wall then i would put them on the end but if not them put them on the back other then that i don't think it matters iv set up a couple going both ways and it dosent seem to make a difference the only thing i found was that dust builds up on the wall behind the hood. you have a nice vent in the back so like jb said make sure they all face the same way and if you put them on the back less wire's to see in the hood. but you have a very nice set up great job.