Canister filters are great, except when an air lock clogs them up. But there’s no need to dismantle the whole thing; here is how to unclog it.
The Fluval FX6 is a beast of a canister. It need water flow to work correctly. When air enters it, the pump will lose its prime, and spin in place.
Fixing the Return Tube Position
You want a method that cycles the valves and power in a specific order. That way, the air goes out via the built-in auto purge system on the unit. That begins with the valve on the end nearest the intake hose. First, grab handle that turns on your water inlet. Turn it off so no more water flows into the line as it builds pressure.
That’s an important first move… Isolating the pocket of air that was trapped in there. The goal is to make a closed space within plumbing system before doing anything else. Then you go to the wall outlet and flip the switch off so that all of the power to the unit are turned off. This shuts the pump down instantly. There is no point in forcing the motor to run if it is air-locked or dry.
Turn it off and have a safe period of time where you can reset the flow dynamics. You don’t want any cavitation damage to the impeller.
Next, you cut power to the unit completely by going to wall outlet and flipping the switch off.
While no electricity is on, open water inlet valve and let the line start slowly refilling with fresh water. It will displace the air pocket that once filled your line.
Here’s when you have to wait a second or two, Gravity takes some time to fill the line. This allows the pump to fire up smoothly, and then it’s time to flip the switch one more time. After filling up your line, turn power back on and watch as the pump kicks back into action and draws water into the canister. Air gets trapped inside. The FX6 will automaticly help push it out (that’s what I mean about an internal mechanism).
As soon as air begins to be ejected, you’ll notice it comes out fast. Then you know it’s working when you watch your sump tank begin to fill back up with water. It’s good to go again and flows well and strong. Keep in mind that the first time through this process will likely only happen if you have just put your new filter in. It takes about a minute for all the air to purge, so it may require a few tries before it gets going.
Let it do its thing, don’t touch anything, for a short period. It’ll typically shut off when there’s no more air. That eliminates having to bleed all the lines yourself, which makes the set-up a lot less painful.
The other frequent problem is where they placed return tube. The intake of your canister sits on top of water and sucks air back into the system. This causes an air lock that just keeps trapping air in the system.
Simply submerge the corrugated return hose so that its joint connecting to the tank is entireley under the surface of the water. That will immediately break the air lock. You want to make sure that the return end is always kept under water. So if you find the tube exposed at all, it’s not by much but that little bit of air can create serious flow problems.
When you get it down there, that fixes the issue. You don’t need any tools, and it really is just a tweakable physical fix where you can simply bend it up or down until it’s underwater. And, you check the joint is still covered by water even if the water level drops a bit. The plumbing setup are stable, so no more air traps will form.
And there you go! Everything just works as it should for the aquarium. The flow rate returns to its normal levels shortly thereafter. There’s no need to make this into some complicated process, and following a few intentional steps would of solved your problem effectively.
