While we're on the topic of water filters, what are some possible ways I can help the water filter in my turtles' aquarium?

I have an aquarium with two red eared slider turtles. It’s a 10 gallon aquarium and I have a filter for a 50 gallon tank (as turtles produce a lot of poo). Here’s the filter I have: Aqua Clear 50 gallon:
http://www.amazon.com/gp/product/B000260FUM?psc=1&redirect=true&ref_=oh_aui_detailpage_o05_s00

The turtles about the size of my hand, so they’re producing a lot of poo. It’s heavy and it sinks to the bottom. It also clogs up the filter. I cleaned the tank two weeks ago and it was beautiful and clear, and now it’s clogging up again.

Cleaning the tank is a lot of work, and of course I will and do clean it when necessary, but it’s time consuming and messy (I usually do it right before a shower, and then take the shower but it takes time and planning). It requires removing the turtles and putting them in the bath tub, and then taking all of the water out and the rocks that are on the bottom, and cleaning and then refilling and putting everything back.

Is there anything natural or unnatural I can do to assist the filter in doing its work? I want the turtles to live in a clean environment so they’re happy and healthy.