I left school for the weekend but before I left on Friday I did a 30% water change, vaccuumed the gravel, added a second cartridge (my filter allows you to put 2 cartridges in at the same time), and put in a fish feeder that i've used before with no cloudiness problem. I normally do my water changes and vaccuuming 1x a week but I was on crutches and had to stretch it to 2 weeks. So I noticed a lot of stuff in the gravel when I was vaccuuming, and I was unable to get it all w/o taking out a lot of water.
So I left right after I did that, and returned on Sunday. My tank has been cloudy ever since. I tested the water and it's fine besides the pH is a bit off (6.0). I used a water clarifier and that did not work like it normally does with tank disturbances (ie: drunk people putting excessive fish food in the tank). I through out the used cartridges and replaced it with one new one. I purchased a little baggie at the store and filled it with carbon to put in the filter with the new cartridge... and it's still cloudy.
I even talked to a very knowledgeable man about my situation and he agrees that it is very mysterious. It seems like I can't do anything else to improve the cloudiness. I have a 20 gallon tank with one fancy fish, and a filter that pumps 30 gallons per hour. I hope the water will clear up on it's on and that my fish will be okay.
I feel so awful just seeing him swimming in it and there's nothing I can do.
...sorry for the long post.
You need to raise your pH first. You can do this with baking soda. I'm quoting Ranchugirl's directions on this, since I haven't yet stored it to memory. 