I have a hang on filter on my aquarium (tetra whisper), but my water is cloudy. how do i fix this?

Bubbles? Or maybe you need a new filter cartridge? Did you add water conditioner? If you have fish in their, it's more then likely their ammonia produced by these guys. Especially if you have Goldfish. I suggest Ammolock. It's a medicine/water conditioner that'll kill and control the ammonia.