How do I best filtrate a kinda overstocked 20g

I have a 20 gallon tank with 7-8 X-ray tetra, 6 green Cory cats, 1 female betta, and 1 platy. I notice my filter gets clogged up easily and the flow slows down dramatically. I have a 20g aqua clear filter HOB and I’m deciding between a 10 g sponge filter or upgrading to a 35g sea chem filter. What is the best decision to take to fix my filtration?