OK did a bunch of stuff yesterday on it. Ok we have the pics up of the plenum, so that did not change, beyond me cutting out the slats. I did put a Rib piece down the center to support the egg-crate however. I then cut out some egg-crate and placed it on top of the unit.
Ok over the egg-crate I put some 300 micron mesh, I was able to buy a 300 micron sock and canabilized it for the project. I glued the mesh to the edges of the plenum with some crazy glue, it had the seem of the bag on top of the center but I don't think it really pertains.
I poured in a full cup of detrius/waste that I had syphoned from my tank, it was enough to cover the floor of the tank. I put in about 22 inched of water also and then placed the plenum into the tank carefully, so the detritus was still evenly spread (4 tries, lol)
From their I bought a bag of carib sea floor sand. I spent a lot of time rinsing the sand as I didn't want the tank to cloud for the experiment. Once rinsed I poured in the sand, I went with 3 inches.
I poured in the water (FW) into the tank very slowly to try to keep the sand from being disturbed, worked pretty well as I could still see the detritus on the underside of the tank. and attached the mag pump to the plenum. So all was ready.
I added some blue food coloring to the water in the tank and gently stirred it so it was pretty dark. At this none of the colored water entered the sand bed. I had the tank set up on two 5 gallon buckets so I lied under it and turned on the mag pump. It took all of 1.5 seconds for the blue water to be drawn into the plenum under space. Caught me off guard as I expected it to have enough resistance to take a little longer, thus I blew the picture with the camera trying to autofocus. The blue die came through the sand surprisingly even. The edges came through just a split second prior to the balance of the unit. I ran the pump for about 30 seconds.
So here are the results as I saw them:
1: The colored water came through fairly even, with the edges showing up a split second prior. The diffusion was a lot better then I had thought and it did pull a lot of what I would call microscopic dust along with it through the bed. I feel you could go anywhere between 2 and 5 inches if you wanted with out loosing this capability
2: The detritus on the bottom of the plenum was removed I would estimate at about 75%. As in their was still 25% of the detritus still present after running the pump for 30 seconds. Although all of it was not removed I do feel it does exactly what it was supposed to do. If you can periodically remove 75% of the build up its has become a maintainable system. Now also my detritus was larger in particulate size then what I believe you would normally get in this unit.
3: Other thoughts, I don't think a larger mesh would be the way to go, better to allow for the solids to be broken down prior to extraction. I think the pump should only be run for about 5 seconds with a tank between 20 gallons and 90 gallons. This is enough time to accomplish what is desired, (the removal of build up under). The use of a strong pump is needed.
Ok that is all that I can think of right now so throw some questions if I have missed something. I am going to try to salvages some pictures.
Mike
didn't know it was tore down for the frag swap. Thanks Mike, now I'll have to go back and reread some,alot of deja vu with the plenum & substrate and undergravel systems of yesteryear.So you have the plenum designed, is the mesh the 250 to 300 you talked about? ,substrate is 1.2 to 2? Must go read.
