Waste collecting in corner drilled overflow

[Galaxie500]

I have a 72g Bowfront with a 20g sump. I received the tank for free a while back so I was on my own for setup. The corner is drilled for a overflow but waste seems to get sucked into the corner but does not get picked up by the tubes leading to the sump. So the waste just collects. I have been sucking most of it out when I do W/C's but I cant get it all and im sure this cant be correct....

Maybe a prefilter?
If my explaination doesnt make sense I can take pics

TIA

 

[chesterthehero]

prefilters are good.. they also keep massive amounts of poop/food from collecting in the sump... just remeber to clean them when you do water changes as they tend to plug rather quickly.. i clean mine three times a week to keep it flowing freely...

 

[Galaxie500]

how do I install a prefilter in drilled tank