Is it normal?

  • We are currently upgrading MFK. thanks! -neo
My emperor 400 did the same thing and about a month later the motor busted. Check your impeller to see if anything is caught in it. I found gunk and a pebble in mine which was what was causing the rattle and louder noise.
 
Sand will absolutly kill the impeller. I had a 350 on a 55g and had the down tube to close to the bottom. As a result (aided by Africans) the sand was sucked up and in. Once the impeller is "scored" its toast, IMO.
I found that placing a spacer under the impeller(a plastic bead my little daughter gave me from her craft box...=) helped quiet it down. Just run the bead onto the impeller shaft. It helps keep the impeller from "bouncing."
 
I have had a 350 on my 46 gallon for 3 years and its never made any noise
 
Ive had a 350 and a aquatech 30-60 same thing no biowheel on mine for 3 years and they arent quiet. the biowheels make tons of noise and the impellers cavitate bad if there is air around. And if you run sand pull the filter of every 3 months rinse it out and pull the motor out and rinse it under high pressure. doesnt hurt to check the condition of that o ring either.
 
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