Yesterday I upgraded my lighting to AH Supply twin 55 watt kits, and added a little powerhead and spray bar for a full bore CO2 mist system. The spray bar is a 5/8 OD by 1/16 wall acrylic tube, with holes about every
1 1/2 in along it's 20 inch length, placed low along the back. I pushed the CO2 tube into the intake grill at the bottom of the powerhead to let the rotor chop up the bubbles. The result is that the tank is virtually full of microscopic bubbles, that look almost cloud like, and the plants all pearl lightly. My measured CO2 is about 50 ppm, using the difference between in-tank and equilibrium PH readings.

Now, my question: the powerhead - made by "Aquarium Systems", model MN-404, about 100 gph output - is a bit noisy. It sounds like a one cylinder motor, chugging away. And, it does this with or without CO2 going thru it. Is there a powerhead available that is a lot quieter and still not overly expensive? I got this one on ebay at a very low price - $5 as I recall. I don't mind the noise from this one, but my wife keeps asking why it's so noisy. I suppose I could change wives, but that would be too expensive.

Change the powerhead, not the wife.

I would suggest a Maxi jet, the mini's are good, I've been happy with rio 90's 180's.

If the bubbles hittingthe impeller is more the issue, then try making the orifice of the intake smaller, this will mean many more bubbles that are smaller, thus they make less noice when they hit the impeller.
Alternatively: using a fine air stone to feed the gas into the impeller will reduce the noise to zero.

Regards,
Tom Barr

It makes the same noise with or without the CO2 turned on, so it seems to be the natural noise of the rotor. Why it chugs I don't know. Thanks for the recommendations.

Incidentally, I discovered today why it is necessary not to raise the CO2 ppm too high. I lost 5 fish and all the others were gasping at the surface. I guess that means the 50 ppm I measured was pretty close to the real value. I shut off the CO2 and the remaining fish recovered well, but the plants kept pearling like crazy for another two hours, before I turned off the lights. Tomorrow I will start with a much reduced CO2 flow.

Using CO2 mist is a goal to reduce the CO2, not go wild with high ppm.

It's to be done slowly and use the pH/KH first, then dial in the rest slowly...........

Regards,
Tom Barr

If it makes noise w/o feeding CO2 into it, there's something wrong with it. Open it up and make sure the impeller is seated correctly and that nothing has been sucked in there.

I used a Rio 50 powerhead (the smallest I could find) and an Azoo diffuser with good results. I placed the input screen of the power head right on top of the diffuser disc so it looked like one unit. The power head shaded the disc so algae wouldn't form on it.

-Russ