powerhead cavitation

[4ptbuck]

I am having problems with caviation in my powerheads which results in microbubbles.

I have 2 802, and a 402 powerhead. I have run each in my tank for several days, and they'll randomly pulse out micros.

Currently I am running 2 smaller powerheads, and these aren't causing me problems.

The 2 802 look to be clean as a whistle. The 402, has a bit of gung in it.

Anybody with any ideas? I want to add more flow in my tanks, but not the micros.

Thanks
4pts...

[tanker]

The bubbles have to get air from somewhere. Put them a little lower in tank.

[4ptbuck]

They are not suck air from the surface.
I am pretty sure it's cavitation causing this.

[143gadgets]

I had a 402 and it did the same thing. No matter how many times i cleaned it, i could never fix this problem. In the end i just went and bought another MJ to replace it and i now use the 402 for mixing my saltwater.

[Randy Holmes-Farley]

I believe that the bubbles (at least the ones that I get) come from cavitation of water that is supersaturated with O2 during the day. The bubbles are then mostly O2. More aeration may help reduce the supersaturation and hence the bubble formation..

[reefdood]

My mj900's on a wavemaster pro does that. Drives me nuts. My 802's never did that in my 90, even on a wavemaker.

[4ptbuck]

Randy, don't you think a skimmer would provide enough aeration to sufficiently drive the O2 gas out of suspension?

[ddenham]

wierd, more aeration would reduce supersaturation, I woulda thought that aeration would maintain saturation, how does that happen?

[4ptbuck]

When a supersaturated liquid is disturbed it will release the gasses.

2 examples, ever hear the story about microwaving a cup of water, and when it is disturbed, it boils over?
or take my fav beverage, carborbonated beer. What happens when you stir said beer? the CO2 in suspension is released...

[Randy Holmes-Farley]

Randy, don't you think a skimmer would provide enough aeration to sufficiently drive the O2 gas out of suspension?

It helps, but in my tank at least, I still see the bubbles during the day and not as much at night, and I believe that it is still supersaturated during the day. It probably depends on the relative flow to the skimmer from the tank, the rate of photosynthesis, and the level of O2 around the skimmer.

[BigBert96]

I am having the same issue with my 402. Every couple of minutes or so, a spurt of micros will pop out of it. Its really an eyesore. Must the powerhead be 100% submerged, or can there be a tiny bit of the top above the waterline? My 402 will only lower so much. I was thinking that it shouldn't matter because the intake is completely submerged as well as the exhaust. Any input would be greatly appreciated!

[Randy Holmes-Farley]

My 802's are clearly not sucking air from the surface. You'd probably get the same result if they were a foot down.

[ejamsrhere]

ok.... I've got the same problem from my hagens and from a power suck (sweep)... My seio 1500 is fine and doesn't do it. I'm sure I have enough aeration between my overflow and my 6' skimmer. I'm pretty sure the bubbles are from caviation .

[BigBert96]

I have a 402 which emits micros. I have a swiveling powerhead (forget the name of it) that is at the same depth, which doesn't do it. Is this telling me that its time to replace the 402? And what exactly is cavitation in regards to a powerhead?