OF with weak siphon

Ok guys, I'm getting bubbles in my u-tube and it's causing my syphon to weaken. I keep getting a giant bubble that is built from small ones hanging out in the middle. What the hell is causing this as I never had this problem before? Anyone got any ideas? Had a similar problem and found a solution or cause?

Thanks in advance!

 

Never had the problem myself (never used an external OF) but i have a couple of friends that have some. They have a small nipple on the top of that U tube with a small air line running down to the sump or attached to an air lift pump. That way the air is always taken out.

Marc

 

Hey rickzster,
Is your return pump matched well to the overflow? Sounds like you need to push water a little faster through the U-tube. I oversize the return pump a little and use a ball valve to regulate flow to push maximum water. Also keep U-tube clean of alge and corraline. Let me know if that helps.
Best, Scott

 

I have a rio 17HF. Pretty fast. But you know, I've been suspecting my return being too slow. Eversince I cleaned it, it's been pretty slow. I might take it out and see what's up.

 

I had the same problem a while back and had to buy a bigger return pump. It worked fine until I increased the height of the aquirium (DIY Stand), then it just could not keep up.

 

You could also lower the overflow box in the aquarium a little. Might increase the flow through the U tubes, pushing all bubbles out.