I've been distributing my CO2 with a powerhead for a month or 2 with good success. One thing that I didn't like with my setup was the sound of the CO2 bubbles being chopped up -- "pssshhh, pssshhh, pssshhhh" (good sound effects, huh? 
) I played around a little yesterday and made the slight modification shown in this pic:
I used to feed the CO2 right into the bottom of the Penguin 660 grate, but now I actually feed it outside of the grate, up near the top. In the picture here, the outlet from the elbow is 3 to 4mm from the top of the grate, but my actual one being used is more like 1.5 to 2mm higher, right near the top of the grate. What happens with the new setup is that the inflowing current pulls off the tiniest amount of CO2 at a time, rather than full-sized bubbles. It has been running today for over 2 hours, and the CO2 is completely dissolving up to this point -- no little bubbles whatsoever coming out of the powerhead. I am using a non-modified impeller also, so the gph is probably at its max.
My elbows have 2 circular ridges which need to be modified with sanding, filing, cutting, etc. so the elbow is right up against the grate. (If you try this and use a razor blade or knife, please be careful. )
Advantages:
1) Easy to do. If you have elbows without ridges (or can easily remove your elbow ridges), you can have this up and running in about 5 mins. You are also making zero modifications to your powerhead, so if you decide you don't like this method, no loss except a few mins of your time.
2) A lot less noise (at least in my case).
3) Virtually complete dissolving of the CO2 (at least in the morning when CO2 saturation isn't complete yet).
4) For those who don't want to or cannot turn off CO2 at night, the CO2 bubbles will float harmlessly to the top, which is good if your powerhead can vapor lock.
For those who may have been thinking about trying powerhead CO2 distribution, this is an easy enough experiment: If you just set up a powerhead in your tank, you can simply hold your CO2 up near the grate and see how it works. No need to go thru the trouble of attaching anything. If you hold the CO2 near the bottom of the grate, you will probably end up with big bubbles. Try holding it near the top with the elbow or connector parallel to the grate (not pointing into it) and see the difference.
) I played around a little yesterday and made the slight modification shown in this pic:I used to feed the CO2 right into the bottom of the Penguin 660 grate, but now I actually feed it outside of the grate, up near the top. In the picture here, the outlet from the elbow is 3 to 4mm from the top of the grate, but my actual one being used is more like 1.5 to 2mm higher, right near the top of the grate. What happens with the new setup is that the inflowing current pulls off the tiniest amount of CO2 at a time, rather than full-sized bubbles. It has been running today for over 2 hours, and the CO2 is completely dissolving up to this point -- no little bubbles whatsoever coming out of the powerhead. I am using a non-modified impeller also, so the gph is probably at its max.
My elbows have 2 circular ridges which need to be modified with sanding, filing, cutting, etc. so the elbow is right up against the grate. (If you try this and use a razor blade or knife, please be careful.
)Advantages:
1) Easy to do. If you have elbows without ridges (or can easily remove your elbow ridges), you can have this up and running in about 5 mins. You are also making zero modifications to your powerhead, so if you decide you don't like this method, no loss except a few mins of your time.
2) A lot less noise (at least in my case).
3) Virtually complete dissolving of the CO2 (at least in the morning when CO2 saturation isn't complete yet).
4) For those who don't want to or cannot turn off CO2 at night, the CO2 bubbles will float harmlessly to the top, which is good if your powerhead can vapor lock.
For those who may have been thinking about trying powerhead CO2 distribution, this is an easy enough experiment: If you just set up a powerhead in your tank, you can simply hold your CO2 up near the grate and see how it works. No need to go thru the trouble of attaching anything. If you hold the CO2 near the bottom of the grate, you will probably end up with big bubbles. Try holding it near the top with the elbow or connector parallel to the grate (not pointing into it) and see the difference.