This will help with your current problem and give you a way to polish the water after any water changes or if you disturb the gravel at all.
Just look for the best price online, and get some diatomaceous earth I usually buy the 5 lbs bag but you can go smaller if you like.
Also when setting it up you will either have to use a tupperware in the tank just below the water surface with both intake and output tubes placed into it so the Diatoms can collect to the bag in the filter, then when the tupperware has no more cloudiness and all diatoms are sucked up by the filter remove the container without turning the filter off and let it run.
Usually takes a few hours depending on tank size and how clogged the filter gets.
I've been using these filters for years as they take anything down to 1 micron in size out of the water(that's 1 millionth of and inch
) so anything bigger than that can be removed.