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Venturi Design

Discussion in 'Estimative Index' started by Tom Barr, Jan 23, 2005.

  1. VaughnH

    VaughnH Lifetime Charter Member
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    Re: Venturi Design

    The flow spirals down. I have a cut-off elbow fitting on the output of the powerhead, aimed to the side, with no effort to make it be parallel to the inside surface of the tube - not enough room to do anything else. I increased the bubble rate a little bit more this morning -- now it is about where it was with the 29 gallon tank, when it fed a powerhead to make mist. Of course I have two bubble rates, with the bubble counter having smaller bubbles and a higher rate than the bubble rate in the reactor. It still spills small bubbles out the bottom, but not small enough to act as mist.

    It may not act like its supposed to, but I get pearling in about an hour now, so it is doing a good job getting CO2 into the water. I think if I put a little air stone on the CO2 feed tube in the reactor I would have a mist system as well as a CO2 dissolving system.
     
  2. Tom Barr

    Tom Barr Founder
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    Re: Venturi Design

    Red Sea makes some nice smaller limewood stones, these are the smallest made.

    "Berlin" limewood stones.

    Even if they make funny sizes later, you can keep 2 and dry and sand one before returning it, should do fine for 2 months before servicing.
    Not sure, though since this might blast the mist out of the reactor also.

    You might have too much flow going into the reactor for the tube size.

    4x2 tube = about 150 gph max.

    Regards,
    Tom Barr
     
  3. VaughnH

    VaughnH Lifetime Charter Member
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    Re: Venturi Design

    The tube I used is 2 x 6, and the powerhead is supposed to deliver 200 gph with zero head. I noticed some limewood stones in a LFS a couple of days ago. I may get one and mount it straight down in the tube, on the end of the CO2 inlet line. I think the swirling water will keep the bubbles confined to the center, but if any escape they are just CO2 mist. My other powerhead keeps a pretty good water current going thru that area, so maybe the escaping bubbles will be effective. The big ones I get now aren't. Still, I have great pearling! GDA is starting up though.
     
  4. Tom Barr

    Tom Barr Founder
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    Re: Venturi Design

    If you see any signs of GDa, nail it asap, don't wait.

    Also, if you clean, uproot, prune etc, always follow that by a water changes s
    soon thereafter.

    That will reduce BBA, Staghorn, GDA and GW chances of getting a foothold.

    Regards,
    Tom Barr
     
  5. VaughnH

    VaughnH Lifetime Charter Member
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    Re: Venturi Design

    There are things we know, things we don't know, and things we wish we didn't know. The need to attack the algae immediately falls in the last category. But, I just did a 70% water change, wiping down the glass to get the incipient GDA off and some pruning.

    But, the interesting thing is that I left the CO2 on for awhile with the powerhead off, so a bubble of CO2 built up in the tube. Now that it is back in operation I have a big swirl of big bubbles at the top, burping occasionally, with a steady stream of bubbles going thru the venturi tube, and CO2 mist!! Now it looks like I expected it to look. I suspect I will be doing this water change/wipe down again tomorrow, because I can see spots I missed.

    As an aside note, my continuous water change system is working like a charm!!
     
  6. VaughnH

    VaughnH Lifetime Charter Member
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    Another update on my Internal venturi reactor use:
    The GDA is in the second week now of a life cycle - just cleaning it off didn't do much to stop it.
    I am still increasing the CO2 bubble rate, trying to find the highest I can run it without affecting the fish. I removed my bubble counter, to avoid that possible CO2 leak source, and because the reactor acts as a good bubble counter. Now I have the rate high enough that a big bubble of CO2 collects at the top, and the powerhead generates CO2 mist all of the time. A little BBA has started on some of the slow growers leaves, which I keep cutting off as I see them. So, as high as the CO2 seems to be running now, it must still be too low. But, the reactor now works just as advertised, and I am very pleased with it.
     
  7. BHornsey

    BHornsey Lifetime Charter Member
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    I built one of these for my 190L corner tank and have been impressed with it; it's efficient and cheap! However it takes a while to get going.
    Just recently I did a water change and turned off the powerhead but forgot to turn off CO2. When I refilled the tank and restarted the pump there was already a bubble of gas in the top of the chamber and it got going straight away and a mist formed much more quickly. Finding an old central heating timer I was able to set it up so that the CO2 comes on about 15 minutes before the powerhead and I find that it improves the start up performance quite a bit.
    Anyone else noticed this?
    Of course, a dual timer is an additional expense and this was supposed to be an exercise in economy but I found it effective.
     
  8. VaughnH

    VaughnH Lifetime Charter Member
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    That's an interesting idea about starting the CO2 ahead of the powerhead. If you have your lights on a different timer than the CO2, as I do, it is pretty simple to simply turn on the CO2 early, and turn on the powerhead with the lights. I also noticed that the reactor gets going good much faster with a big bubble of CO2 already in it, but I also noticed that the effect only lasts about an hour, before that big bubble is used up. Then it settles down to the usual operation, which is good. I will try this pre-charge idea right away.
     
  9. BHornsey

    BHornsey Lifetime Charter Member
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    Yeah, that's a thought. I have mine coming quite a bit ahead of the lights so as get CO2 levels up before the lights come on.

    At the moment, I just tried 15 minutes of CO2 before firing up the powerhead. The lights come on later still.

    Let me know how it goes.
     
  10. underwurlde

    underwurlde Junior Poster

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    I would love to be able to build one of these magical little reactors, but am having trouble sourcing the bits.

    I live in the UK which never helps.

    Could someone please tell me where I can get those powerheads from (beit in the UK or US) or at least a suppliers part number.

    TIA,

    Andy

    PS
    Part numbers / suppliers of all the other parts would complete this guide IMHO
     
  11. BHornsey

    BHornsey Lifetime Charter Member
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    Hi Underwurlde, I'm in Doncaster.

    I got mine from Swell UK Underworld Aquatic Systems Maxi Jet Powerheads 400 - 1200 but I'm sure most places do them. I like the Underworld Aquatic pumps.
    The tube was an old gravel vac that I got from Pets @ Home and I used a wooden air block on the CO2 delivery tube

    Brian
     
  12. CodFather

    CodFather Junior Poster

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    Design link

    Hello just subscribed to the site. Love the layout and fuctions of the site/forum. Thanks for all of your hard work. I am interesting in the External DIY reactor but the link is sending me to a screen stating that a new version of hte site has been opened and that the team is looking forward to seeing me there. Maybe it's just my pc? Anyone having any success with the following link?

    http://www.barrreport.com/gallery/browseimages.php?c=11

    Sorry my first post is about the link. I'll properly introduce myself soon.

    CodFather
    :)
     
  13. Tom Barr

    Tom Barr Founder
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    It does it when I clicked on the link as well.
    There are several places that have a DIY external, notably Rex Grigg's site.

    I'm without a camera dn time pinched at the moment, I will some day get around to DIY pic projects and post the gnarly versions I've designed for several applications.

    Does not help you today though:D

    Regards,
    Tom Barr
     
  14. ccLansman

    ccLansman Guru Class Expert

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    Sorry to dig up and old post but i just really wanted to say thanks Tom for this amazing DIY. I just got mine up and running and for the first time ever have plants that are pearling like crazy. I did a few modifications but the design is almost exactly like you had it.

    Thanks!

    -Chris

    Here is the venturi in action:
    ImageShack - Hosting :: 1004194gb6.jpg

    "the cool drag effect is due to the slowness of my cheap camera :D"'
     
  15. Tom Barr

    Tom Barr Founder
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    Thanks for the movie thar:)

    The difference can be amazing when you tweak the CO2 CORRECTLY.

    Everyone thinks I'm nuts about CO2, but you see the largest most dramatic differences when you add this fertilizer.

    And once you see spectacular pearling and growth, you should sit down and remember it.

    Then remember it again.
    Just keep that one parameter in mind when anything goes sour.

    Tweak that before trying anything to do with NPK.

    NPK, Ca, Mg, Traces can be easily reset and tweaked(Large water change+ dosing them to non limiting levels asap afterwards). You KNOW those are in good shape after doing that.

    The light is the same.

    So that only leaves one variable in question: CO2.

    The intense pearling and growth, without harming any fish, is the "test" that you have good CO2 once you rule out the nutrients/traces/lighting.

    Thing is, measuring CO2 via the pH/KH has trade offs, same deal with the Drop checker, and bubble rates are not any better.

    The best measure is really the plant growth rates/O2 production.
    It's indirect, but it does measure precisely what we want to grow.

    CO2 is funny, it can change dramatically in a few minutes, same with flow rates, and other parameters that are important to CO2/O2.

    Regards,
    Tom Barr
     
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