i have a 6100 i just took out of the box and got it setup last night and was running perfectly for about a little over 5 minutes , now from that point on its been humming every time it kicks on . it is set at 100% and 30 % . my wife has already commented on the noise so i'm just curious if this is normal to be heard out side of the tank because i could only imagine what it sounds like on the inside the tank . i also have a 6200 i have not taken out of the box yet because i not sure if i want to deal with this type of humming noise if it is normal . thanks in advance