I did all of my research before setting up my 150 gallon mbuna tank...however, there is one thing that I forgot to research and that is how to clean/maintain a wet/dry filter. I have pfs for substrate with large river rocks for hiding spots. My stock is currently at 16 including a bristlenose pleco. I made my wet-dry with Tupperware containers. I've noticed my nitrates are starting to rise faster. I replace my filter floss (quilt batting# about once a week. Last night I swished and squeezed the pot scrubbies #bio balls) out in a bucket of aquarium water and did a water change expecting my nitrates to go down quite a bit. They used to run in the 10-20 range....now they are between 40-80. Should I replace some of the bio balls periodically? My tank has been up and running since May with no problems. I'm trying to be proactive and prevent problems. I would love advice from someone who successfully maintains a wet dry filter. Thanks in advance!