I hate these HOB overflow filters.
That being said, those are getting clogged fast.
Upping your filtration is going to fix your water quality.
You don't LOOK that heaviliy stocked
How big is a 'Medium' fish?
Please tell me you're not using Play Sand
you can see from how popular HOB filters are on the site that they do exactly what theyre intended to so long as the proper size is bought. for that reason, I really doubt you're expensive filter cartridges are getting clogged so fast. I don't even use the commercial filter cartridges with my HOB just some floss and carbon/zeolite and ive never had an issue with water clarity.
You might wait for some other opinions b4 running out to by a new toy, but like i said b4 green water comes from one place. a UV sterilizer is available at just about any fish store, and the cost will depend on the size you get.