Another method for CO2 diffusion: needle wheel powerheads

Today I modified my Maxijet 600 to be a CO2 mist machine! I used a small finishing nail to melt only three holes per blade, but they are much bigger holes than a needle gives, and I made sure no holes overlap from blade to blade. Then I took an airline size piece of acrylic pipe and plugged one end with acrylic cement-the high viscosity stuff. Just before it was dry I poked a needle hole thru the center of the cement to get a very small hole for CO2 to bubble through. This I used acrylic cement to glue into a hole I drilled into the intake tube for the powerhead, so it acts like a crude venturi. I connected my vent line from the external reactor to that. It is now running in the tank, giving a faint buzz as each CO2 bubble goes through, and the tank is now seltzer water. The added circulation is still considerable, even with the drilled paddles. Now I need to adjust the CO2 bubble rate so I don't kill the fish.

I like this much better than the Barr Internal Venturi reactor - it is much smaller, no clear tube to grow biofilm on, and it really generates the CO2 mist, with CO2 that would otherwise just sit in the top of the external reactor. I'm a fickle "lover" though, so I may get over this love affair too!

I have a Rio 800 (RVT), but I can't figure out how to get at the impeller ... I'm afraid I might break it. Anybody have any clues?

The powerheads I have worked with have a twist off compartment that holds one end of the rotor. You have to be able to get to the rotor, because you need to clean it and the inside of the driving coils or it eventually locks up. The removable part is the part with the inlet (center) and outlet (outer) passages. I had to use a pair of pliers, gently, to turn the one on the Catalina powerhead so it would come off.

Yep, that's what I have ... hinged flexible blades. The hinged blades sure seem small. I could probably get 9 holes in each one if I used a needle (and was very careful). If I go with a 1mm size, I'll probably only be able to get 4 or 5 holes in each one. I might alternate blades and do a combination of both sizes of holes. I'm wondering if a sewing needle sized hole would even do anything ... perhaps it's too small.

Why wouldn't this work?

I've been looking into trying the needle wheel method for distributing CO2 with a little powerhead. However, I've been wondering why a simpler solution would not work and I cannot think of one.

I have a canister filter. If it is strong enough, could I modify the impeller to be a needle wheel and then simply run the CO2 hose directly into the filter intake in the tank (just put a hole in the prefilter and run it thru)?

tedr108;22576 said:

I've been looking into trying the needle wheel method for distributing CO2 with a little powerhead. However, I've been wondering why a simpler solution would not work and I cannot think of one.

I have a canister filter. If it is strong enough, could I modify the impeller to be a needle wheel and then simply run the CO2 hose directly into the filter intake in the tank (just put a hole in the prefilter and run it thru)?

Click to expand...

I do exactly that, except I haven't bothered to modify the impeller of my canister filter. I get complete dissolution without any buildup of CO2 in my canister. It's like an inline PVC reactor except that it happens to have filter media in it. It's worked well for me, so I've never wanted anything more complicated or involved. Simple is good, right?

What different will it make if you let the gas up thru the intake of the powerhead ?
Do i get even smaller bubbles if i drill a hole in the side ?

/A

tested today

Well, I converted a Rio 800 RVT to a needle wheel and tested it out today for CO2. I was conservative on the number of holes in each blade (since they are small), alternating 3 in a line and 2 in a line, so 3 of each pattern on the six blades -- I alternated them so no holes were lined up from blade to blade. With the RVT there are 2 venturi loop inlets built in, so no modifications were necessary for this, which is nice. I run the pump upside down (with the intake on top) because I wanted the CO2 bubbles to come out just below the filter output to help in dissolving them.

If the drop checker is a good indication, this worked incredibly well. I had been running my CO2 thru my filter inlet recently and was getting a good green on the drop checker thruout the day. However, this method seemed to push the drop checker to a yellowish green with the same bps. I really feel this method rivals the DIY external reactor, and it is simpler, so I like it. The other advantage, of course, is that the little powerhead really increases the flow in the tank as it is distributing the CO2.

Now, in the back of my mind I'm wondering if the drop checker is a good indication. With all of those CO2 bubbles floating around, how many bubbles nestle under the drop checker and explode into the drop checker ... perhaps giving me a false green. I have my drop checker on the opposite end of the tank away from the CO2 pump, so I'm probably safe. Anyway, I'm going to go with this method for a while and will know soon if I have enough ppm or not.

One thing that may bother some folks about this method, but not me, is the constant flow of tiny CO2 bubbles floating around the tank. At this point in time, I actually like the look of this, and the fish (and plants) don't seem to mind.

(P.S.) It should be noted that I borrow some sort of a drill from a friend that can drill very small, perfect little holes to do my needle wheel modifications. Think a slightly bigger version of a dentist's drill. Compared to what some guys are going thru (heating needles and nails and melting holes in the impeller blades), I have it very easy in this regard.

If I were to adapt a tiny powerhead 2inch square size. where do I feed the CO2 hose into?

Would this do a good enough job on a 125Ltr tall? (30inches long)

I assume we are removing the diffusor in this method? I currently use a Rhinox 2000 which although good does lag off by the end of the week as per Tom's statements about disc diffusors.

Andy

What's important is your powerhead's gph. For a 125 liter tank, I would say that 150 gph powerhead would be alright, easily -- maybe you could go as low as 100 gph -- if I'm wrong about that, somebody please pipe in here.

Each powerhead has a different design and there is not just one answer to your other question. Most powerheads do not have an air hose intake, so you have to put a hole someplace. In mine I was able to drill a hole in the bottom of the intake basket slightly smaller than the air hose elbow and it fits very snug. I can also put a 1/8" piece of air hose over the elbow from the inside so it will stay for sure.

If you do not have an intake basket, but just a housing that goes over the impeller with intake grates on the sides, you can drill a hole either just under the impeller (if the impeller is not too close to the housing) or simply go thru one of the grates. Again, I drill just big enough that my air hose elbow or straight connector just fits ... and then I'll put a tiny piece of hose over that from the inside.

Hope this helps...

I was thinking of using a maxijet MP400 so maybe this would make things easie for you to explain to me. lol

I can grasp most thing but never owned a powerhead or pump before.lol

Andy

Andy,

That looks like a good choice. I looked at an online picture of the Maxijet 400 (I hope the "MP" isn't a different model, I did not see that one) and my guess would be that you can easily feed the CO2 in thru the bottom of the pre-filter screen -- just barely insert it in, so you don't cut down on flow much. Like I said in the previous post, you may want to put an air line elbow at the end of your air line and put that thru the pre-filter. You drill just big enough for the elbow to fit into the hole.

That is the easy part. Now you need to find a way to chop up the bubbles.

Method 1: What is normally recommended is that you put a few holes in each impeller blade -- don't overdo this as you do not want to reduce flow too much. Keep the holes in the same location generally on each blade, so the impeller doesn't become unbalanced. You can either get a very small drill with a drill bit at or under 1mm or you can heat up a needle and push it thru the impeller blades. With the hot needle method, you will probably get some strings of melted plastic left over -- cut or sand those off the impeller.

Method 2: This is the method I use, but I am probably the only one using it. My powerhead has a design very similar to the MJ 400. I feed the CO2 into the bottom of the pre-filter. However, to make things simpler, I did not modify the impeller blades at all. I simply cut a small piece of no-see-um netting, removed the pre-filter, put the no-see-um netting over the intake tube and put the pre-filter back on. So, now the powerhead is pulling in water and the CO2. When the CO2 hits the no-see-um netting with the water, most of it is dissolved in the water and some very fine bubbles are formed too. This is working very well for me. Luckily, I had some no-see-um netting on hand (I'm a backpacker). With this method, you really need to put an extra pre-filter over the plastic pre-filter, because the no-see-um netting will probably clog up in less than a day without it. I use a rather fine filter floss padding and sew it into a cone shape (by hand) with a hole in the bottom so I can feed the CO2 thru it.

The pump Andy refers to has a venturi already present, therefore avoiding the need to drill any holes, at least that's my understanding is this going to effect the design or the effectiveness of the design at all?

The venturi on the Maxijet 400 powerhead, as with most, seems to come after the impeller -- it is at the outlet. I would just plug that hole. The CO2 must go thru the impeller for this method to be really effective.