different powerhead "reactor" for CO2
This post is related to this thread (but different enough to warrant a new thread, I figured):
I had a Penguin 660 Powerhead on hand and tried a very easy modification last nite that is working extremely well for distrubuting my CO2 -- please see the attached picture...
First of all, I drilled a 3/16" hole in the bottom of the conical grate and feed the CO2 into it thru the airline elbow -- airlines are different sizes, I am sure, so you can simply drill a hole slightly smaller than your elbow -- the grate is somewhat flexible (so be careful drilling).
I still didn't like the idea of modifying my impeller because I found even a couple of holes in each impeller cut down flow, and I'm sure some folks just didn't feel comfortable trying impeller modifications at all. Anyway, I simply pulled off the inlet grate and put a very small piece of no-see-um netting over the tube and put the grate back on. The impeller is untouched. I am getting the smallest bubbles you can imagine ... most of my CO2 is completely dissolving.
Advantages of this method:
-- simplicity of modifications (one hole and one piece of netting)
-- increased flow (my 170gph Penguin 660 is putting out about 4 times (a wild guess) as much flow as my 185gph Rio 800 RVT with venturi inlets with 2 or 3 small holes in each impeller -- it may not be 4 times, but it is very significant)
-- extremely efficient (probably because the impeller is not having to deal with big bubbles, which seems to really increase flow) -- I've already reduced my bubbles per second for the CO2. I first reduced my CO2 bps count from 3 to 2.5. My drop checker was still going yellow, so now I've reduced to 2 bps. This is on a 50G tank.
Disadvantages of this method:
-- it sounds like a clock, though not extremely loud (every time a CO2 bubble goes thru the powerhead -- there is a "psshhh, psshhh, psshhh"
-- although the 660 seemed totally silent at first, there is now a little noise after running for 6 hours, though it is still quieter than my external reactor was
-- Possible disadvantage: not a long enough test yet, but no-see-um may clog (using a pre-filter over the grate will help -- I use a very fine "floss" type of filter pad -- sewn into a cylinder or cone shape) -- I'm willing to clean it once a month, but more than that would get old. Too bad a pre-filter is needed, because the inlet cone grate is a very good bubble counter!
By the way, I did make one more modification that is not really necessary. The cone inlet has 7 sizing sections ... I cut the top 4 off and left only 3 as the top 4 served no purpose -- leave at least 3 for sure, they are helpful and necessary as that is the part that goes over the tube. This makes it easier for me to put on a pre-filter ... it's smaller and I have a lip to tighten the pre-filter around.
This can easily be done with any powerhead that has a downward pointing tube as an inlet ...
In the attached picture: no-see-um netting, Penguin 660 and sample airline tubing with elbow to go into bottom of grate.
Hope this helps someone ... definitely working well for me.
Last edited by tedr108; 02-22-2008 at 02:47 AM.
If you take a lighter and melt and taper the tip of the airline/CO gas line, you can get even smaller more consistent bubbles spit into it and reduce the noise and increase the efficacy.
Basically heat and pull the plastic tip until you get a very small diameter
What materials have you done that with? I don't think it would work very well with vinyl airline hose, because I think that stuff burns pretty close to it's melting point. Maybe the semi-rigid polyethylene stuff?
Originally Posted by Tom Barr
If only I had a glass pipette or capillary...
few more thoughts
OK, OK, my initial enthusiasm about increased flow was a little overblown because my powerheads all seem to slow down after running a while -- maybe they get hot and friction slows them down? Anyway, this "reactor" is still working very efficiently and doing its job well, but the flow isn't exactly creating a whirlpool either.
Sometime in the next fews days I'll try Tom's idea of creating a narrow nozzle by heating and stretching the air tubing. Heck, I might not even need the no-see-um netting, if I can get the nozzle fine enough. Now, if I can find somebody that works with glass tubing, I would like to have them make me a cool little glass nozzle, like Swylie is talking about -- I'll bet that would work very well. Get the right sized glass tubing and it could slide right into your air hoze ... that sounds very nice.
These Penguin 660s do not hang straight when used with a suction cup -- they are actually meant to be under-gravel filter pumps and should be sitting in a tube. If you put the back up against the glass, it will hang straight one way, but I had to sew a sponge on to the suction cup side to get it to hang straight up and down. It may be my imagination, but it seemed to run quieter after that -- either the sponge insulation or just being straight up and down.
Lastly, a fine pre-filter over the inlet grate is definitely needed with this method. I ran it without a pre-filter for about 6 hours and I would say that the no-see-um was about 1/4 clogged after that time. I'm using the bonded blue/white filter padding (from Marineland), I hope that will be good enough -- it's fine, but doesn't seem to reduce flow much. I use it on all of my filters as a pre-filter and clean it once per week -- it seems to grab a lot of dirt and very fine stuff, my filters never get dirty.
Last edited by tedr108; 02-22-2008 at 05:11 AM.
Yes, use the ridig air line tubing, hard to do with the other.
We use the same method with glass to make extremely fine cell probes. Works pretty well actually even t such small diameters.
The other thing you can do is modify the intake vane of the suction side of the powerhead to make it a slight venturi intake, basically reduce the size of the inlet by about 1/2.
Yes, this reduces flow some, but creates a powerful venturi in this region.
Adding a tapered rigid air line for the CO2, and some holes in the impeller(impellers are cheap BTW, do not worry so much about them), now you have a pretty turbo charged powerhead.
I think the Maxi jet series are pretty good and this is the unit I'll use on most of the tanks I have set up in addition to the in line venturi/needle wheel.
This will give me spot CO2 treatment and see some effects with mist vs the other method.
Yeah, I've pulled glass stirring rods before, and I used to date a neurobiologist, so I've seen the glass capillary electrode pulling machine. Had a sign on it saying that the professor would kill you if you messed with the settings. Heh. From what I know, single-cell recording electrodes are made from glass, and those are so fine it's ridiculous.
Originally Posted by Tom Barr
Glass is super-easy to work with, but it's so fragile that I wonder whether it's actually useful for our purposes. I was only half-serious when I suggested it. I'm going to fire up the blowtorch and give the PE tubing a try.
Sorry for derailing your thread, tedr108, I only commented on this thread in the first place 'cause I think your idea is interesting.
I'd simply stick with plastic acetates....the diameters we need for a given flow rate and the durability works well for the plastic.
Well, I tried pulling PE tubing, and I managed to get some pretty small orifices. Some were 300 micron or so, but I managed to get one or two that were in the 50-100 micron range. I'm just estimating visually here, so those numbers aren't necessarily tremendously accurate. The blowtorch was a poor choice for this project though. I had much more luck with the cooler, broader heat from a kerosene lamp. You have to carefully heat the plastic to just past the plastic temperature and vary the pull rate as the plastic cools.
I'm not sure how small a bubble these openings will produce though. I guess that depends on the velocity of flow past the orifice. With no flow, you still get pretty big bubbles because of surface tension. I should do some calculations on the pressure required to drive air through such small openings I guess to see how many I would need to feed my tank.
Well the strenght of the tip also plays a large role, no good ifthe gas flow breaks it or you damage it.
You can use larger walled tubing and then just mash it and poke a tiny pin hole in that. It'll be tough.
would it work if you used a rigid airline tubing, placed a sowing needle in one of the openings, heated it up until it melted around the needle and then remove the needle? Is that opening large enough to run the co2 through?