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Re: NFC: Under gravel filter

> nickel55 wrote:
>                           Can anyone tell of a good site that tells and
> shows how to make an underground filter. I already know about buying pea
> gravel for the substrate and getting one of those ceiling light fixture
> covers for the gravel to rest on, but I need a little more instruction.
>                             Thanks for any info.

Making such a filter is hard to justify, unless you have an unusual tank
shape to work with. Inexpensive UGF plates with risers and airstones are
available for most rectangular, square, and hex tanks. They are cheap unless
you time is worth less than $0.10/hr. By the time you buy the parts, it may
be even worse, as the parts might cost *more* than a finished, well-designed
filter, and yours might not work very well.

I'm not sure how you are using the ceiling fixture cover, so can't comment
sensibly there. Fitting proper risers with top screens and air-lift
diffusers to a regular flat plate cover would be rather tricky. It must have
free-flow space beneath it, too.

I have used 1/2" cpvc pipe, elbows, and tees, to build an undergravel tubing
grid like they used to make commercially 50 years ago. Tiny holes, drilled
every inch at about 30 degrees from vertical into the bottom sides of the
pipe grid allow water to flow in without sand or gravel clogging them. 

BTW, pea gravel is at least 2-3X too coarse for aquarium filter use. You
need about #12-16 mesh water-smoothed aquarium gravel for that. With the
cpvc (NOT pvc) system I have even been able to use #30 sand-blasting silica
sand. You can put a little coarse gravel over it for appearance if you like.
The cpvc unit cost me several times what a commercial UGF would have cost,
but it did let me use the finer sand. I've found a sheet of the fiberglass
cloth used to lay up boats, etc., can be placed across the top of a
commercial filter and will allow very fine sand use, too.

Sorry, but I strongly suspect that the low price of commercial units has
made it very unlikely that any DIY (do it yourself) sites are out there.
[C'mon folks. Prove me wrong. ;-)]


Wright Huntley, Fremont CA, USA, 510 494-8679  huntleyone at home dot com

                There are two rules for success in life:
             Rule 1: Don't tell people everything you know.

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