Why does my fish tank always look cloudy

The "levels" are always good when I test the water. But I get an algea buildup fast and the water is cloudy. Help!

You don't mention how long you've had the tank running, type of fish, color of the "cloudiness", or what parameters you're testing, all of which would contribute to giving you an accurate answer.

If your tank is new (running for less than 2 months) and the cloudiness is white, your tank may still be cycling. This is when you have bacteria multiplying quiclky to take advantage of the ammonia produced by your fish which they use as a food source. The ammonia is toxic to your fish, but the bacteria convert it to nitrite (also toxic), then to nitrate, which isn't toxic in moderate amounts. As long as there's more ammonia and nitrite than the bacteria can convert, they multiply at a rapid rate, and this can give the water a cloudy appearance (what's generally called "New Tank Syndrome"). Once the bacteria are present in enough numbers that all the ammonia and nitrite are being converted, the reproduction will slow and the cloudiness will go away on its own.

You can get prolonged periods of cycling if you try to clean the tank too well (thinking this will remove the cause of the cloudiness, but in reality, all you're doing is reducing the amount of bacteria so they continue to reproduce). You should only be doing partial water changes (15% twice a week to 25% once a week or as water tests show necessary). Overfeeding also contributes because extra food=extra poop, and excess food also produces ammonia as it decomposes. In both of these cases, the cloudiness will appear white.