Is the outlet of your tank a single nozzle ?
if it is then what I did was to get some flexible tubing and some rigid tubing. Put the flexible tubing over the outlet of your filter and connect it to a piece of rigid tubing. The rigid tubing needs to have a few holes drilled in it along its length and be secured above the water using suckers. One end needs to be blocked off
Once connected up the water is sent down the tubing and is squirted out of the holes back into the tank across the surface of the water - you can keep extending it using more flexible hosing to go round corners and more rigid (pre-drilled) tubing to make more spray bars.
I'll see if i can find a pic
http
/www.animalworldnetwork.com/cainfiwispba.html
here you are - the small picture to the right has a spray bar attached to the filter outlet nozzle