a few things you can do:
1. switch to a less messy food.
2. change at least 1/3 of the water every week (not week and a half

)
3. add an AquaClear 110 for excellent mechanical filtration that can be rinsed weekly. your rena can do most of the biological work..
4. feed 5 or 6 days per week rather than every single day. if you are feeding high protein foods, your fish grow well, but its messy and its good to give them a day to 'purge' their systems a bit. At least, I always do with my (former) monsters..
5. check your water parameters (ammonia, nitrite, nitrate). often, a cloudy tank is a sign of an readable ammonia or nitrite reading, which is bad..
hope this helps!