7400 and micro bubbles

[pedalpower]

Hi Roger,
I have had my 7400s for awhile now and just recently I noticed that a lot of micro-bubbles are being shot out of them. Both powerheads are completely submerged, so I'm not sure where they're coming from. Is there something I can do about it?

Thanks!
Joe

 

[rvitko]

Check that they are clean, this comes from a combination of chemistry issues and internal pump vacuum. If the pump is clean the vacuum is reduced, be sure to check the center hole in the magnet for obstructions. If your KH is high or light intensity is high it is a gas saturation issue particularly if you run an RDP refugium or have lots of macro algaes and fast growing corals. In this case lowering KH and reducing photoperiod are the only remedies.

 

[pedalpower]

I checked the impellers and sure enough the hole in the back had build up on it. I cleaned it off and it's back to normal.

Thanks!
Joe

 

[pedalpower]

Well, turns out that cleaning the pumps did not help. I should say that really only one of my pumps has the problem. Also, previously I had them in a different location in the tank with the same parameters and did not get any bubbles. What are you considering high KH? My KH is ususally around 8.8 and I run my lights for 7.5 hours (250w 10k over a 90 gallon). I do have a refugium but all I have in their right is a softball size piece of chaeto.

Thanks!

 

[rvitko]

KH over 12 degrees usually and 10 hrs or more of light or just alot of algaes. Sounds like it is just an issue of positioning, some how it is taking in air where it is. Maybe you could lower it more?

 

[pedalpower]

The powerhead is about 3/4" under the surface of the water. The other one which does not have a problem is only 1/2". I don't see how it could get be getting any air. What would the signs be for when the impeller or bearing needs to be replaced?

Thanks!

 

[rvitko]

How old is the pump? If it is 3/4" but turbulent or a cross current is present that facilitates a vortex this could be the cause.

 

[pedalpower]

It is less than a year old. I run two 7400s in each corner, pointing to the opposite corners. They are set to 30%/100%. I have the interval in the middle setting. I also have a filter pod on the problem PH. So the current isn't excessive. I noticed today that the bubbles appear at

 

[pedalpower]

Sorry, I didn't finish. When the pumps where in there previous position they both had the flow deflector on. But, when I moved them I took the flow deflector off. So, I just put the deflector back on and no more bubbles.