Funnily enough, I was reading your thread just after I had posted mine, and thought the same thing. I have had tanks with sumps in the past and its much quieter than those, but Its far noisier than I would have ever expected.Hello Paul. Deja vu for me. Not sure whether you’ve seen my previous posts re 850t. Long story short , you’ve described my filter. In the living room but loud enough to hear upstairs and regular air purge. We ended up turning it off if we wanted quiet time. Oase suggested new impeller. No change. Dealer agreed with my suggestion of swapping 850 head with 600 head. Bought 600 head for £59.99 with promise of refund when I returned 850 head.
Unfortunately 600 head only marginally quieter, I think. Interestingly the clips fixing the 600 head required far more effort to engage than on the 850 which seems to explain why the 850 purges air, and the 600 doesn’t at all. Also the flow rate seems very similar in terms of water movement within the tank.
Regards, Ian
When I spoke with Oase today, they accepted and conceded straight away that there has been air trapped in the 850t, so it's clearly a common problem for them.
I don't want to turn this post into a slagging off at Oase, as the file ris performing admirably in the filtration department and the customer service has been exemplary. I was merely venting my frustrations. I am far more miffed with Aquael and the utter garbage level of service from them.