You can build a skippy filter (lots of links on here, checkout the DIY - Do It Yourself - section) and put things in it for bio filtration, like pieces of 1/2-1" clear tubing cut into small pieces, scrubbie sponges, anything that will help catch stuff from the pond, and keep it from going back into your pond. You use PVC pipe and send the water from your pump (on the bottom or close to the bottom of your pond) up to the top of the Skippy filter, then pump it to the bottom, where it will push upward through the filter media and bio media, then flow out the top (check out the home-made waterfall weirs in the DIY section, or classifieds, too!) over the weir or something to make it flow back into your pond. You can also attach a pipe or two or three at the top to let the water flow through back into your pond.
I think the only PVC with rock on top that would help would be a bog of pea gravel, where the water is pumped into the bottom siphons up through the pea gravel, then flows back into the pond. You plant the bog with all sorts of water loving plants, and their roots will absorb the waste from the fish and use it up, therefore keeping it from being food for algae. Check out Addy's Bog thread, maybe DIY section? She is the queen of bogs!
Good luck! And, if your pond person didn't help you, find someone else, or keep asking questions on here! Be patient, that's the name of the game this time of year. I have two ponds, one is crystal clear now, the other is still very murky. Pond dug last year is murky, one dug this spring is clear, started out murky. They will all clear up with enough filtration and patience.
