First off, New pond and complete filter clean, yep you goofed. Now lets work on the question at hand. first off if the pond is a month old and your getting green water, stop feeding as much, Your getting way to much much for that early in the ponds balance, I promise the fish will not starve. Second, NEVER clean your filter with city water or water hose. You can use a small pump and pond water and do just as good of job and the water will be safe for the bacteria. NEVER clean all your media at once unless your getting ready to shut the pond down for winter. Otherwise you want to clean part of your filter and preferably the prefilter more often until you don't catch so much muck in it. As for back flushing. You should run the water until it clears for the most part, but you may need to backflush often to catch back up with the build up you have already accumilated. NOW for the good news. in most ponds the pond itself can contain as much bacteria as the filter so revuvinating the damaged bacteria bed won't take as long as the process is already under way in the rest of the system as well. A good way to back flush the filter is also by taking a 5 gallon bucket of pond water and flushing it backwards through the filter while the backflush valve is open. takes a lot longer but safer on the system than a water hose. Last but not least, Are you testing your water for ammnia, nitrite, and nitrate? If not you really need to start, your at the critical point in the balance of the pond that you need to monitor closely as the ammonia will spike soon, when it does it's a good idea to do 20% water changes to keep it under control until the rest of the sytem catches up. If your pond is big enough and your fish load light you should cruise on through this inital new pond syndrom in about another moth of so then it's smooth sailing. feed less, check water, do water changes and most ponds are pretty forgiving.
