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Fluval 407 microbubbles

Krackar

Feeder Fish
MFK Member
I've been trying to find the cause of microbubbles from a Fluval 407 that is running on my 75gal tank.

I bought the whole package second hand and everything was clean and ready to use. I have 2 407's running on the tank. After setting it up and cycling the tank i added fish and have been trying to find the cause for over a month. It was driving me crazy. I changed the main seal o-ring, the aquastop o-rings. I changed the intake and output hoses. I thought the filter container was bent out of shape due to how it was stored before I bought it. so had a clamp trying to maintain a better seal.

I finally read about the intake strainer having a ball valve inside it and it could affect your flow rate. It caught my attention as i thought the output of both my filters was a bit low. I was not aware it even had these. I checked them both and found a lot of old plant waste blocking them both. I cleaned them out and had an immediate large flow rate increase and the microbubbles disappeared.

From what I understand the suction from the pump was greater than the intake could supply and was drawing air in around the seal! When the pump was off I was unable to find any leak to indicate where the break in the seal could be. I was looking for a leak that didn't exist unless the pump was running.

Hopefully this will help someone else at some stage. So clean those intake strainers regularly!
 
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