ok i was cleaning my tank and accidently left the filter on. apparently, some sand has entered the filter (aquaclear 20 gallon) and now my filter is making a strange noise. it sounds like someone with a raspy, just-caught-a-cold voice. while before, it was very quiet. when i opened up the filter, i saw bits of sand and cleaned out as much as i could. but it is still making the noise! do i have to completely replace my filter or can i make it go away? ANY help would be appreciated. thanks