My fish filter wont stay working help!!?

well is jus evry couple of days i have to clean it out and i dont wanna keep doin that well wuts happenin is like it has an extra slot so the water if it gets too ful it goes out through there but the problem is evry couple of days the main slot were water comes out is cloogged with nothin!!so then i have to go clean the nothin out of it and theres some fish **** but not nearly enogh to clog it on the walls so i have to continualy clean it out well it came from walmart with a lifetime warrenty on the box so would they exchange it without a reciet? i might have it somwere but would they exchange it well here r my fish in a 20 gallon tank i got a pea striped eel a red claw crab a koi 2 bigish goldfish and a see through fish also 2 crayfish real small so plz help wut should i do?!