Streams blowing bubbles?

[jeffbrig]

Roger,

I've had a pair of 6100s on a 7095 running for at least two months now in a new system. Periodically, I notice one of the streams will blast a mass of air bubbles into the tank. I'm trying to identify the cause of this. The streams are mounted at the lowest position on the mounting rails, and are NOT drawing any air in from the surface.

There are a small amount of microbubbles present in the tank at all times from my return plumbing, but I can't see any way for those to be collecting inside the stream pump.

My more recent theory is that they may be the result of cavitation, as they seem to be created when the stream surges from 30% to 100% power on the controller cycle. Is this a reasonable possibility?

Thanks

 

[scenaria]

turn off the return pumps to elminate microbubbles in the tank... then turn on the streams to see if the bubbles are still there.. my bet is they wont be..

 

[jeffbrig]

I'll try that tonight to see if it makes any difference. Who knows, but I would be very surprised if the amount of air I'm seeing could collect inside a stream while it is running.

 

[rvitko]

It could be that you have a saturation of gas in the water and then the pump could degas this excess from the slight vacuum inside.

 

[dougc]

Miy 6100s blow bubbles when they go to high speed. I have slightly reduced the upper speed to mitigate the problem. It does seem get worse when the pumps need cleaning.

I think that the only real solution would be to have the controller accelerate the pump more gradually. I don't know what effect that would have on the beneficial turbulance created by the pumps, though.

 

[rioreef]

I just have a 6060 and is at the lowest point on the hanging bracket Tunze provides and have the same situation you are describing. I traced the situation - every now and then the unit will create a vortex on the surface and a mini-tornado forms. Now not every time, but this will be drawn down all the way to the unit and presto...a blast of bubbles comes shooting out of the pump.

Not of the micro variety, so they quickly rise to the surface and break. Entertainment for the fish.

 

[Lutefisk]

I have had the same thing rioreef describes. You can hear a "slurping" sound when it occurs.

The shroud (cowl) around the impeller has a grating over about 270 degrees. You can minimize this happening by making sure the portion of the shroud without a way for water to enter is pointing towards the water surface.

Paul

 

[ssbreef]

I have the same problem coming from my 6000 but not my 6100. No slurping or pulling in air from the surface. If it where a gas problem than my 6100 would be producing the same results, but nop no bubbles from the 6100. What could be the cause?

 

[rioreef]

Is the 6000 near any other source where say microbubbles a sump return enter the tank? This may accumulate in the 6000 under the shroud as described by Lutefisk and at a point is sucked out by the blades.

Just a thought?

cr

 

[rvitko]

The other possibility is the 6000 is dirty, if the hole in the center of the magnet is plugged a strong vaccuum will build up and degas the water. Older models also were more prone to this so if it is 2 or more years old it would be a good idea to buy a new drive unit to get the upgraded unit with a vacuum break.

 

[ssbreef]

well the have both only been in my tank for about a month now, and they both are starting to get coraline algae growing on them, could this be the cause? What hole in the center magnet ?

 

[rvitko]

It could be the coralline, in very high calcium/KH environments you could havee precipitation within a month in the pumps. In the center of the magnetic rotor is a hole that cooling and lubricating water passes through, this gets fouled with sand and lime deposits over time and must be cleaned.

 

[ssbreef]

Ill check that out.

 

[DownUnder-Reefer]

Mine (6100's) do not suck air from the surface but have always blown bubbles.

 

[cirri]

I am having the same issue, has done it from the beginning. I actually believe that since I have my cover rotated facing upwards to elimate the problem from surface suction, it is actually increasing it by giving the air somewhere to be trapped. When enough bubbles get sucked back in to the tunze, wham they burst out everywhere.

I was going to turn the cover to have solid portion facing downwards to see if that helps.

I know I read that having the cover towards the top helps this situation, but I am curious if everyone that has this issue is set the same way.

 

[rioreef]

I have rotated the cover so the 'solid' portion is on the downward side of motion of the blade. This is to have the slotted portion venting on top, but limiting the downdraft from the surface on the other side.

Seems to help in the elimination of bubbles, but not all. Make sure as mentioned earlier, keep the unit cleaned.

cr

 

[cirri]

unit is clean, and only 2 months old (already soaked 2X's). Like I mentioned has done this out of the box. Had no micro bubble in the system prior.

I want to completely elimate these bubbles, and seems you did what I was thinking, but still present huh?

 

[rioreef]

Not as many now. I have seen the bubbles excaping from the top without any vortex forming on the surface extending down.

 

[cirri]

No choice but to give that a try I believe.

 

[rvitko]

Just my experience here- if your pump is making bubbles and it is not from vortexing you really should double check the hole in the magnet rotor for obstructions, your KH and your light intensity/duration. If the bubbles get worse as the day light hours progress it is definitely a gas saturation issue and removing excess algae, cutting back on lighting and lowering KH are the remedies. If the pump has any obstructions to the cooling system, the internal vacuum increases and more degassing occurs.