Fluval FX5 keeps bubbling!? Help please!

[RustyGrizz]

So I used to have this FX5 hooked up to my 300gallon just as backup/extra filtration but the tabk is already setup as a sump system so no need for it really and it worked just fine, then I got a 120 gallon and decided to use for that tank. The first couple days it was hooked up I had no issues then after that it started to constantly burp and send out micro bubbles all the time. Only thing I had changed was after a week(bubbles were already an issue before hooking this up) I put a sponge filter on the intake(as pictured) with no air, because my fish were spitting gravel into the intake and it was getting sucked into the canister. So I read up if you have too much filter pads/polish pads this could happen. I did have foam over top of bio rings on first layer then phosphate filter over bio rings on 2nd layer then carbon over top of bio balls in 3rd layer. I decided to remove foam/phosphate/carbon filters so all I have are the typical sponges on the side of the racks and then just bio rings and balls(gravel that had been spit into filter was removed as well) and it still bubbles. I also checked for any leaks and to make sure every think is sealed properly and i don't see anything. If I actually unplug for an hour then plug it back in i have to bubbles for 4/5hours but then it starts to bubble and burp again. Soon I'm at a lose, have no idea why its doing thing. Anyone out there know why this is happening? TIA

 

[deeda]

Air trapped or getting into the filter is usually because it is getting into the intake connections somewhere. Is the connector over the rim of the tank below the water line? I can't see it in your pic.

How are the hoses running from the canister up to the tank, any loops or sags?

 

[Jacob92677]

I had similar experience
My intake hose was catching air At the water line I needed to tighten the hose clamps
I’d check hoses and clamps are tight
It’s seems like it’s pulling air in somewhere

 

[Oscar Mike]

I also just purchased a used fx5 and put a sponge on the intake so sand wouldn't get sucked up. What I found was the pump is so strong that once the sponge gets a little dirty it blocks the suction creating loss of pressure. This causes the pump to cavitate which occurs when the liquid in a pump turns to a vapor at low pressure and spits out bubbles.

 

[TheWolfman]

It's cavitation from that spounge filter choking out the canister. In a closed loop like a canister the intake and the return need to be the same. If the return is out performing the intake you will get micro bubbles. You might want to look for a more corse spounge for that intake or get rid of it all together.

 

[RustyGrizz]

It's cavitation from that spounge filter choking out the canister. In a closed loop like a canister the intake and the return need to be the same. If the return is out performing the intake you will get micro bubbles. You might want to look for a more corse spounge for that intake or get rid of it all together.

The thing is it started to do the bubbling before I installed the sponge to the intake. However for the sake that I'm at a lose, I Uninstaller the sponge and put the stock intake back on and sure enough within a few hours its bubbling again. I've made sure all the hose clamps are as tight as possible and the canister lid screws are also as tight as I can get.

Is it possible the sealing ring on the lid needs to be replaced even though there is now water leaking or air being drawn in that is noticeable? Or could some gravel have damaged the impeller which is in turn creating bubbles in the canister?

 

[Oscar Mike]

Don't overtighten the screws or the lid can become deformed and won't make a tight seal. The plastic piece at the bottom of the screw breaks easily (temporarily using a c-clamp in place of one of mine that I'm pretty sure was already broken when I bought it). Cavitation can also be caused by packing the trays too densely or using filter floss.

 

[RustyGrizz]

Don't overtighten the screws or the lid can become deformed and won't make a tight seal. The plastic piece at the bottom of the screw breaks easily (temporarily using a c-clamp in place of one of mine that I'm pretty sure was already broken when I bought it). Cavitation can also be caused by packing the trays too densely or using filter floss.

Yah when I got this pump the lid was a little deformed and some screws have broken off the bottom piece but I'm able to wedge a screwdriver in the bottom when I tighten to hold the screw in place. However the lid is a little deformed. If it wasn't sealed properly would I feel air being pulled through the seam of the lid or would there be water leakage?

Trays are packed densely all that is in them is bio rings and bio balls then the stock foam filters on the side of the trays.

 

[TheWolfman]

Open up the filter and give it a cleaning. If your using the foam in the middle of the trays remove that and just keep the regular media in there. Inspect all of the seals on the quick connects and around the lid. If there are broken clamps on the lid replace them as necessary.

 

[FJB]

Air is getting in from somewhere. Is there a chance one of the hoses has a very small crack between ribs, or a pinch hole? Air could be getting in very slowly. Otherwise the clamps or the top seal. I can't think of other sources.