AC 30&70 Trouble

[Bennlfer]

Hi i recently changed stock in my 20G long and now my AC 70 and AC 30 are making this weird high pitch humming noise. I think its from sand getting in them. They still work with almost the same efficiency but they are LOUD. I have taken them apart and cleaned the propeller as best as i can, but to no avail Any suggestions on how to fix them? I dont want to lose 2 filters at once.. Thanks.

P.S. I have already removed the sand from the tank to try to help.

 

[Edwardo]

It sounds like you need to replace the impeller, about $10.
Anytime Ive had trouble like that with my ACs , 9 times out of 10, changing the impeller usually does the trick.