Noisy or inconsistent pumping is usually caused by air lock-ins or incorrect priming of the filter. Always follow the setup instructions to the letter. There are a few videos and tutorials in circulation that show a wrong priming process, resulting in reduced pump performance.
All external filters are mainly gravity fed (and then utilise a pump to pump the water back up). The pumps are not designed to actively pump water out of your aquarium, so we need to have a reliable gravity flow in place. External filters always have to be positioned below the tank level to assure a constant gravity feed.
The process of filling and starting the filter is called "priming". For the exact steps, please consult your manual.
For exact steps follow the manual. In general, the process is similar for all external filters. Make sure the filter is not plugged in (running an external filter without water will damage the unit, this is especially the case with thermal filters!).
1.) Install all the pipework and valves (make sure all valves are closed)
2.) The filter has to be empty (DO NOT fill the canister with water before installation/priming!)
3.) Open both valves (in and out)
4.) Pump water into the canister via the prime button (mechanics vary by model and manufacturer, see manual!). This can take a few minutes.
5.) When water stopped filling the canister, give it a few shakes to dislodge any trapped air. A couple of additional presses of the prime button will help
6.) Plug in the filter - some additional noise is normal at this stage. Now give the filter a few more shakes. After that is should run normal.
Air lock-ins can happen naturally, especially after maintenance or when there is an air pump producing bubbles near the filter inlet.
In most cases, this can be resolved with a few presses of the primer button and a few shakes of the canister. If this should not solve it, you might have to prime the filter again, which includes closing all valves, unplugging the unit and emptying the water from the canister. Then follow the instructions above.
Other causes of reduced pump performance
- Please check the tubing for kinks or dents (tubing should be cleaned or replaced from time to time since it will fill with algae and dirt
- Check any pre-filter sponges or inlet/outlet guards for blockages
- If there was a power loss recently, the filter might need priming (see above)
- The impeller can wear over time and will need replacing at a certain stage. These parts are not covered by warranty, but your retailer can help you source a replacement part.