I have posted a few times now about my New 75 Gallon Tank. I finally got the water in it and been running it through the filter and starting the cycling process. I have noticed the Fluval 406 Canister Filter, which is normally pretty quiet, occasionally makes a slightly louder flushing sound. No air escapes into the tank when this occurs or anything and it seems to be in working order. I am brand new to canisters having only had the hanging ones on my smaller tanks. I was just wondering if this a normal thing with this type of filter. Did I miss something in setup??? Thanks!