Iam getting a strange noise coming from my Eheim 2236 ecco every few minutes.....It sounds like a swooshing noise...almost how my dishwasher sounds.....Is it air in the filter? I never stopped it from running since I got it 2 months ago and never brought the intake above water....I haven't cleaned it yet because I dont think its that dirty...I have a 29 gallon with the Eheim and 60 gallon hob whisper....Iam just curious to what this noise may be.....It just started doing it....And I really don't wanna mess with the eheim too much because I have heard so many horror stories about this fragile plastic handle cracking off while trying to open it.....If any one can help it would be appreciated