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Re: Materials for filter fittings - a chemistry question
The way I have set up a similar system on my fry recirculating system is to use a length of PVC gutter that rests on top of the sump (a 55 gal food grade drum). I put ends on the gutter and cut a hole in the bottom. Onto that I glued a short length of PVC pipe, 1.5" diameter, which sits over a hole in the top of the drum. I placed a plastic mesh screen over the hole to prevent the media from falling through. I then made a spray bar from 1.5" PVC pipe. It has a T in the middle, fitted to a 1/2" barb/screw fitting, that screws into a reducing adaptor on the 1.5" T. Many small holes are drilled in the bottom of the spray bar. Water drains from the return line from the fry boxes to the spray bar, then drips over larva rock placed in the gutter. In such a system you want your media to be porous to increase surface area and to be just slightly wet, covered by a film of water. The latter maximizes oxygenation, favoring the bacteria that you want to convert ammonia and nitrite to ni!
trate. Good oxygenation should make the fish happier too.
In a fry setup like this, the amount of water returning can be small, which means the spray bar might not drip enough to wet the larva rock. I made an airlift out of a piece of clear plastic pipe with a 180 degree bend on the end. An airline enters this through a hole drilled in the side and lifts water out of the sump (the drum) into the spray bar through a hole drilled in the top. That way, plenty of water drips over the larva rock, no matter how many or few fry boxes I have going at any time.
Barry
At 11:48 AM 3/7/2002 -0500, you wrote:
>In a message dated 3/7/02 10:54:45 AM, William_Vannerson at ama-assn_org writes:
>
><< And I would think that it's not as strong, but I believe that it would be
>more waterproof.
>
>So a question to the chemists out there, is either material, brass or nylon,
>better suited for a filter system?
>
>Bill, I can say without any doubt that nylon will probably not work due to
>its capacity to absorb moisture and distort (similar to acrylic in that
>respect). Stainless steel will not rust if the proper grade is chosen. Brass
>will introduce copper to your system, which may be good or bad depending on
>the concentration. I would suggest white oak. It is pretty water resistant
>and non bending if thick enough and is easy to cut to shape. It may discolor
>with time, but who cares?
>
>Lee Harper
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___________________________________________________
Barry J. Cooper, Prof., Dept. Biomedical Sciences, Cornell University
Current address: 27505 Riggs Hill Rd.
Sweet Home, OR 97386 (bjc3 at cornell_edu)
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