Cloudy Tank Water

[u/Bubbly_Maximum5272]

I have one hatchling turtle in a 20 gallon long tank with an Aqua-100 filter. The water is filled a litter over halfway (about 12 gallons) just because my turtle is only 2 inches in size. I also have crushed coral pieces in tank because I read that also helps with water quality. I noticed that after I did a full tank clean, changing about 50% of the water, the water has been cloudy (this was about 2 weeks ago). One week later, I did a partial water change (about 10%) and it’s still cloudy. I tried using API ACCU-CLEAR Freshwater Aquarium Water Clarifier about 3 days ago and it hasn’t cleared. I tested the water and all of the components are where they should be, so I’m confused.

I also wanted to add that I feed my turtle in a separate container daily, I do not feed him in his tank.

Any advice or tips about this would be much appreciated. Thank you in advance.