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Experimenting with external undergravel filter.


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I've been looking into the efficiency of undergravel filters lately.  It's very "old school," but seems to have a lot of advantages.

In my reef keeping days, I used a very deep sand bed as a sump (18 inches).  I was able to remove my protein skimmer and have no detectable nitrates.  Now, we don't shoot for anaerobic conditions for freshwater.  However, the external nature of the deep sand bed got me thinking.

What about a rubermaid sump, with some PVC piping and uplift tube, powered by a bump at the top.  Water flows down from the main tank into the sump, and the bump bulls from the PVC piping and returns it to the tank.

The piping is covered with 2" of pea gravel, followed by 8" of sand, and another 2" of pea gravel.  That would give a huge surface area for ammonia-to-nitrate filtration.  The pea gravel at the top allows detritus to quickly sink down from the surface.



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Cool.  I went ahead and got the PVC.  I'm wondering if I'll just make a tank and run it with the UGF or if I try to replicate the experiment that I saw and see how high I can push the ammonia-to-nitrate handling.

I do love the idea of an external filter that is super simple.  I've got a couple of different pumps.  I will probably set things up with the depth of substrate that I mentioned and see if the pumps actually work (whether they can draw water up through the substrate without issue).  Once I've got that working, I'll decide what direction I want to go in. 🙂

Another interesting idea is to let the UGF run for a few years and then connect up a newly set up one, run it in parallel for a while, and then retire the original...

Edited by Galabar
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