Need opinions on microbubble issue

[highrpm]

Need help with Microbubbles
I have been working for 3 weeks to try and get rid of the microbubbles in my new tank. I have a 180 AGA RR, 1 1/4 durso's to 1" drain to the sump and fuge. I have a blueline HD 40X external pump for the return with 1" out of the sump to the pump. 1" out of the pump to a 1" to 3/4" tee, this feeds the 3/4" return lines going up each overflow, which is then attached to a spray bar across the entire back of the tank. I do the a 90 degree elbow on the intake side of the pump, inside the sump facing down.

I have put filter floss material, and filter sponge in front of the last two baffles in the sump, trying to get the last of the microbubbles. The causes the pump to suck more air, due to the decreased flow through the sump. If I restrict the pump using th ball valvles, it helps but doesn't eliminate the problem.

I have two ideas I might try, wanted to get some expert advice first. The two files labeled option1 and option2 are my ideas.

Basicaly I am thinking about adding more distance between the sump and the return pump inlet. Let me know wat you think.

Thanks

 

[highrpm]

Top view of sump

 

[highrpm]

option 1 - the green piping is the new/questionable part

 

[highrpm]

option 2 - same thing, green piping is the new part

 

[John_Brandt]

Highrpm,

Adding plumbing length to the pump intake probably won't solve the bubble problem (if bubbles are entering the plumbing, they will remain regardless of the plumbing length) and may actually make things worse.

I would suggest a few things that are applicable to any bubble problem. First, position the tank drain plumbing as far away from the pump intake as possible. This is also true for skimmer drain plumbing. These two sources of bubbles (tank and skimmer drain) are the most common origin of microbubbles being pumped into the tank. By placing maximum distance bewtween these and the main pump intake you allow many bubbles to rise to the surface and burst before being sucked in.

Secondly, I would suggest you re-seal all of the connections on the intake side of your main pump. If there is a small leak the pump will often draw in air (a good analogy is a pinhole in a drinking straw...you always get air when you suck on a punctured straw). Make sure they are plenty of wraps of teflon tape if this is used. I see a ball-valve on the intake side of your set-up. The main valve stem, and sometimes the union-seals will leak slightly on some ball-valves. I recommend you lubricate and retighten any o-rings within the unions of your ball-valve. Again, any small plumbing leaks on the intake side of an external pump will often lead to air bubbles being sucked into the flow.

Another possibility is simple cavitation. When powerful pumps with strong vacuums are used on saltwater there is always the chance for cavitation. This probably occurs where the vacuum is greatest, just outside the actual volute or within the impeller housing itself. Gases dissolved in the saltwater will spontaneously form larger bubbles, not unlike the effect seen when opening a carbonated beverage. A common contributor to cavitation comes from using narrow pump intake plumbing. Always use the same diameter plumbing as the pump volute throughout the intake line. IOW, if your pump has a 1" intake, then use 1" plumbing on the intake side. Restricting the intake line will increase the vacuum and promote cavitation. In extreme cases cavitation can be dangerous to the animals.

Cavitation can be identified and remedied by slightly closing off the ball-valve on the outlet side of the pump. Only close the valve enough to stop the formation of bubbles. This cuts the flow volume slightly, but most importantly reduces the vacuum. Never adjust the intake side ball-valve to control water flow, as this will often cause cavitation.

As an aside, your sump design has one of my pet peeves :wink: That weir (divider or baffle) in front of your pump intake basically creates a sump-within-a-sump which allows your pump to draw air long before the sump runs very low on water. That baffle seals off the remainder of the sump when the water level drops to the height of the baffle. I sometimes drill holes in these baffles or cut them out to eliminate that effect.

Preventing and stopping microbubble formation in reef systems is often a real challenge. Do some things and report back, as we can probably help you fix it if it persists.

 

[highrpm]

John- thanks for all the input, that gives me a lot of ideas to try. I will let you know what happens

 

[cdeakle]

I'm having problems with all the micro bubbles as well.

Quick question,

Are these bubbles actually bad or just bad for viewing purposes?

 

[John_Brandt]

Microbubbles can be harmful under certain circumstances. They can cause a supersaturation of gasses that could lead to exopthalmia (pop-eye) in fishes and even something like the 'bends' with bubbles forming in their tissues.

Microbubbles can also irritate some corals and cause them to remain contracted. I've also seen bubbles forming inside the tissues of corals from this.

After having said all of that, in most cases it seems thay they are just a distraction for people and not a real problem for the tank inhabitants.