Nitrate battle
I have a 34G solana and I consistently have nitrates between 20-40ppm.  I  do 5-10G water change at least once a week and they still stay in that  range.  
I need some realistic advice on how to combat nitrates to consistently  keep them lower.  I know that since I don't have a sump they will never  be zero but I would like them to be lower than they are.  
I currently have next to no algae, I feed once a day.  My chambers run as follows:
Chamber 1: tunze 9002 with cup mod
Chamber 2: filter floss, purigen, CPE, phosban, chaeto. (in that order top to bottom). 
Chamber 3: ATO, heater, return pump.  
Any help would be awesome!!
Thank you.