To treat "cloudy" water, you must first try and understand what was the cause of the clouding. If you are starting "pre-bloom" algae, you may have too much light (maybe some stray sunlight at some point during the day?) or too much nutrient in the water. Planted tanks benefit from a few fish, but your fish load may be too much for your tank. Rule of thumb is 1" of fish per gallon of water MAX (you can have LESS). In the case of some cold water super-polluters, like goldfish, it is 1" of fish length to 4 gallons of water.
Other causes of "Cloudiness": When you change your filter medium, try and do it in steps. For instance, if you have 2 pieces of foam or plastic filter mesh, change one, then change the other in 3 days. This will give the new filter a chance to re-seed with beneficial bacteria from the one older filter you left in. Changing water with your filters all at once at the same time could potentially reduce your bacterial coloy to levels too low to handle the excess fish food and waste, etc., in which case "undesireable" bacteria may start to gain the upper hand (kind of like "new tank syndrome").
If you just throw in an air stone and it drops your CO2 levels rapidly (by off-gassing CO2 with the oxygen bubbles that are leaving the water), your pH will also alter rapidly. This sudden pH change can cause discomfort, illness, and even shock (or death) to some or all of your fish, so do be careful!
When you change your water, the amount and frequency can sometimes have an effect on cloudiness. Minimum changes would be 3 times a month, but even better is 25% a week, or 15% to 20% twice a week. If you go too long without a change your tank can become sceptic which is toxic to fish and not good for plants. If you change water too much or too often (say, like 50% every week, and 100% once a month) you can reduce the colony of beneficial "nitrification" bacteria that your water needs in order to keep ahead of the "bad" bacteria in keeping up your nitrogen cycle (breakdown of ditrius and uneaten food, etc. -- ammonia to nitrite, and nitrite to nitrate). If you have a well-established tank that is broken in and aged a bit, you may also be benefitting from the "de-nitrification" that comes from certain anearobic bacteria that convert accumulating nitrates into harmless nitrogen gas that escapes into the atmosphere.
I hope this helps. Come back if you have more questions. There is no place around here like this place, so THIS MUST BE THE PLACE!