Tired of HOB overflow

If it's possible to increase the flow of your return a bit, the overflow will drain faster and pull those small bubbles completely thru before they can collect and make a danger bubble at the top of the u-tube.

 

Do you have microbubbles in your display tank?

I would not recommend the CPR continous overflow myself, prone to failure unless you keep the additional aqualifter pump running all the time, a U tube is much more reliable in this case.

What size overflow box do you have, what diameter U tube and what is your flow rate? FatBastad may have hit on something, low velocity can be an issue sometimes with any HOB design and you may need a single tube if you have two or a smaller one if you have a single.

 

I had this issue when I was using both Utubes on my PF-1000 with around 500GPH going through them. Once I took one out, no bubbles ever collected.