J Tube Issues

[Noob]

Wanting to see if you all could give me some possible reasons why my J Tube on my HOB overflow is not holding the suction.
I get the water flowing through it, a couple hours late a bubble forms then continues to grow until the water is barely trickling through.

What could be the problem?

[Andresm]

maybe ur return pump is to small to handle the flow. might need a bigger return pump

[Big_Pun]

anything in the tank making a wave like vortech or tunze wave box, is there a return or a power head pointed at the over flow box. box may set to high and flow may be slowing down and causing bubbles to enter the box. if you take some pic or even a video of it running that would help. its been a while since i have messed wit a hob overflow box, so im just throwing stuff out there that's happen to me

[Mike]

Small crack in j tube letting in air?

[Noob]

Small crack in j tube letting in air?

Thats what im thinking also, because the flow is good and there is not waves.

[Mike]

Pull it out, turn it up side down and fill it with water and see if get any leaks. Maybe leave it propped up as with a very small crack, might bead up slowly. HTH