Welcome to AquariumAdvice, iluvindigo! (so do I)
Please do not take any of my comments as attacks--I'm just trying to be concise. They should help!
You've got a bacterial bloom in your tank. Billions of little bacteria have stopped colonizing the surfaces in your tank, and have taken to the water, because there is so much nitrogenous waste in it (i.e. Ammonia, Nitrite, and Nitrate). Bacterial blooms are common for new tanks, esp. when 1) someone has overfed the fish or 2) when large fish are kept in a tank that's too small for them. Sounds like the former might be the case.
It doesn't matter how much filter power you have on a tank if what you're trying to filter out is smaller than the holes in the filter media. You're trying to get rid of bacterial in the tank, and bacteria can only be filtered out by a diatom filter (filters out everything larger than 2 microns (2/1000ths of a mm!).
**One solution is to get yourself a diatom filter online at bigalsonline.com. It'll cost you $69, I think. Vortex makes the most reliable one for your size of tank, called the D1. Hook that up to the tank, and it'll be crystal-clear in 10 minutes. It's a great filter to have around the house for when tanks are cloudy, or when you can see particles agitated into the water column by the fish.
**The more thorough option is to gravel vacuum (do you have one of these?) the substrate of the tank until you can't get any more muck out of the tank. Do this every 1-2 days with a siphon, and take out about 50% of the water each time. At the same time, reduce feeding as much as possible. As the waste leaves the tank, the levels of nitrogenous waste should reduce. When the bacteria don't have this to "eat", they'll die back to the surfaces. In a tank, you always want good bacteria on the surfaces, but never in the water column.
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A big issue here is that you're not doing water changes *nearly* as often as you should. 20%-50% of the water should be changed every 1-2 weeks to keep your fish healthy, and to keep nitrate levels in the tank down. Ultimately, it's nitrate that will lead to bacterial blooms. Why this hasn't happened to you in the past is a bit of a mystery!
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Hope this helps.