Filter/Aerator Unit

Discussion in 'Catfishing Library' started by BKS72, Jun 24, 2008.

  1. BKS72

    BKS72 New Member

    East of KC
    It’s that time of year again – the blue bite is slow and I’ve decided to try and catch a flathead or two. One of the keys for the big brown uglies is frisky live bait. As you know, keeping bait alive and well as water temps climb is a true hassle. Since the weather is a bit rough here today and I’m too cheap to drop the money on a store-bought set up, I decided to hang out in the garage and make a good filter/aerator unit.


    As water gets warmer (lets say above 75F or so) its ability to hold oxygen diminishes greatly. As a double-whammy, the warmer water increases fish metabolic rates, causing them to need more oxygen. Throw in the stress of being caught and thrown in a tank, and they need even more oxygen. Another side effect of stress is an increase in rate of excretion (think of the kiddie section of your local public swimming pool), causing elevated ammonia levels in the water.

    The idea behind an aerator is to increase the amount of oxygen in the water by bringing more of the surface area of the water into contact with the air to allow more oxygen to be absorbed into the water. There are a lot of ways to do it but I decided on using a venturi set up to “suck” air into the water and then put the bubbles as far down in my well as practical. I decided on this approach after quite a bit of research for a couple of reasons.

    1. Lots of small bubbles increase the amount of water in contact with the air, allowing more surface area for absorption of oxygen.

    2. The longer the bubbles are in contact with the water, the longer time available for oxygen to be transferred into the water and for CO2 to be transferred from the water.

    3. I hate listening to a noisy spray head spraying water, I like to use cool, clear, dechlorinated water from my garden hose to fill my well so I can see my bait instead of re-circulating 80 or 90 degree opaque river water.


    4’ or so of half inch PVC pipe and 4 90 deg. fittings
    Filter media
    Activated Charcoal/Ammonia reducer
    2 quart container with lid
    3/8 plastic tube
    Teflon tape


    Drill with 3/8 bit
    Razor knife
    Half inch hole saw


    The first thing I did was made my venturi. This is pretty simple and the same principle used in a carburetor to pull fuel into the air flowing through the carb throat. We’re going to do the opposite, use the venturi to pull air into liquid.

    To make the venturi, just take a short piece of 3/8 tube and cut an angle on the end. The pix below show how I made mine. I drilled a 3/8 hole in a piece of pipe, wrapped my tube in Teflon tape so it would fit snug and not leak, and inserted it into the pipe. The open side of the tube is the outlet side; the closed side is the inlet side. As the water passes around the closed side of the tube, it creates an area of low pressure behind it, sucking air down the tube and into the stream of water flowing past.




    The next thing I did was to screw the pump base onto the lid of my container after test-fitting and marking it to make sure the pipe would exit where I wanted it to. Pix are below.


    Then I put some filter media around the pump inlet to keep debris out. I used zip ties for this, but I’ll be changing those out for a rubber band as soon as I find one to make it easier to remove and clean. See above picture.

    Next step is to make my charcoal/ammonia reducing filter bag. I swiped one of my wife’s knee-high stockings and filled it with the charcoal mixture (available at about any pet store) and tied it off. Be sure to leave it loose enough that you can squish the filter around as needed. This also provides weight to make the unit sit correctly on the bottom of your well. Picture is below.


    The next thing was to drill water inlet holes and the hole for our pipe in the container. I used a 3/8 bit because that’s what was on the drill and I’m lazy, but to reduce debris getting into the filter lots of smaller holes would work better. I also prefer the larger holes because I want all the junk in the water to get pulled in and trapped in the filter media, removing it from the water.

    Then I put some filter media in my container behind the inlet holes, arranged my charcoal filter around the pump, and put the lid on the container.


    Then I assembled my venturi unit and outlet pipe and tested it.

    Pictures of the assembled unit and the unit working are below.