Microbubble advice
 

Hello,

I am having a slight micro bubble problem with my tank. It is not too bad but I want to eliminate them completely. First I will tell you about my setup and it would be great if you found the cause.

The tank is 130 gal. and the sump is an ADHI 30 which I assume is 30 gal. in size. The return pump is a mag drive 9.5 where it is pumping about 4-5 ft of head. I am also using a 100 micron filter sock on the drain. There is also a baffle in the sump and I have this filled with mesh bags of carbon.

My concern is that my return pump may be to strong for the setup and is what is causing the bubbles. What do you think?

I agree with your accesment,

that is a pretty big pump for a 30 gallon.

So you think thats too big for the sump huh? Is there anything I could do instead of changing the pump?

Depending on the layout of your sump you could make that pump work. I have a 20H sump with an Eheim 1262 for a return pump.

How many baffles do you have after your drain? Are the configured for a bubble trap (Over / Under / Over)?

Here is a link to a pic of my sump and I have the return on the right side.

[url]http://www.championlighting.com/product.php?productid=22061&cat=0&page=1[/url]

Yup... get a smaller pump.

Why do you think it is to large of a pump? On another thread everyone is telling me the pump should be fine?

You can T off the return line and divert some of the water back into the sump. You can also install a valve to reduce the flow going back to the display tank.

Do you see bubbles going into the pump? Are you using the dreaded foam on the intake side of the pump? I'm just making sure you're not starving your pump.

Mag 9.5 flow varies dramatically depending on how its plumbed. If it has 3/4" tubing, it should be OK. 1" would be on the high side, larger than 1" would be too much.

Actually that pump might even be small for a 130 gal tank and the manufacturer recommends piping of 11/2" diameter!
The first question I would make is if you are using the pump pre-filter, if you do remove it, it causes pressure drop in the inlet that makes the pump create cavitation ending up in micro bubbles.
Also insure that you have no leaks in any part of the piping from the pump to the main tank, finally insure that the water level in the pump compartment is as high as possible, higher level will creae postive suction pressure which will also prevent cavitation.
I think having the carbon bags in the baffle compartment may be making the water level too low in the pump's compartment by blocking the water transfer from one compartment to the other.
Finally if the tank is relatively new (less than two months) water tends to have some more surface tension while the sand bed and other areas create bacteria that may process some of the organics, that may create some more bubbles for a while.

I wouldn't call a Mag9 small for a 130G with a 30G sump. Using the 3 - 5x rule, thats 390 - 650 GPH. A 30G sump is not very big, so I'd stay on the low side of that. Close to 400 GPH is a lot of flow throgh a 30G sump. Yes, you need 1.5" plumbing to get the full flow from a Mag9. Most people dont, and few even realize this. Most plumb it with undersized plumbing which dramatically cuts back the flow. Same as putting a ball valve on the output. With 3/4" plumbing, it is in the range of flow where it should be. If it has 1", it would be on the high side. 1.5" definitely too much.

At a 4-5 feet height with 1" pipe there will be about a 6 to 6.5 feet of head pressure on the pump and 8 feet head using 3/4" pipe under ideal conditions. By the performance curve the actual maximum flow with a clean newly installed pump will be 700 gph (see curve below) with an actual real flow of around 600 gph which is the typical flow for a 55 to 60 gal tank with a 1 inch drain and relatively low volume for a 130 gal tank.
That sump design is rated for a flow of up to 1000 gph

I use a 40 gal sump and I am running around 3500 gph trough it in my 330 gal system.

[IMG]http://www.reefs.org/library/pumps/pumps/mag9_curve.jpg[/IMG]