filter problems


Lifetime Charter Member
Lifetime Member
Nov 21, 2007
Los Angeles, CA
Figures this would happen on the weekend, when I can't call support...

I am running a Fluval 305 on my 50G tank. (I also have a Powerhead running much of the time during the day to increase flow.) The filter is only one month old. Last night, my filter started giving off bursts of bubbles every few minutes or so, and they are loud and very annoying, esp. in a bedroom -- there must be a leak someplace. I have checked and tightened all hose connections. I checked the main O-ring and hose O-rings, and they all seem fine.

I read in the manual that you should lubricate the O-rings, but they neglect to tell you what to lubricate with! I have some "silicone oil" that was used with an old copier. Is this OK? Is there anything else I can use? I seriously doubt this will make much difference with a new filter. I don't want to hurt my fish or plants. I can run to the LFS easily enough.

I'll call Hagen on Monday, but would like to try anything that might help before then. Any ideas? I'm going to dismantle and clean the filter, but I doubt that will do much.

Thank you in advance.

(P.S.) I actually bought a Rena XP3 as a backup filter a while back when I found them on sale for $89. I'm tempted to go with the XP3, esp. since it has a higher gph rating and will increase flow in my tank.


Prolific Poster
May 23, 2007
Silicone oil will be fine. Safe for the fish, safe for the rubber gasket.