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Re: UGFs -- Use Gravel for Filtration

Scott H reviewed some of the maintenance issues with UGFs, and did so well
and thoughtfully.  The one factor he did not stress even for FO tanks is
that novices tend to set and forget these units or adhere to the myth that
the units need no upkeep as they are bio-only.  To that could be added the
factor that these were invented in the days before powerheads as air driven
units, and now tend to be hugely overpowered with massive powerheads, which
compounds the clogging issues.

But the reverse flow situation, using prefiltered powerheads to push water
down the tubes and back up through the gravel all but entirely moves the
mechanical filtration aspect to the prefilter, removing the debris build-up
and compaction issues from the substrate.  If the sponge prefilter is
maintained, the substrate can operate as biofilter indefinitely without

I have never been a fan of UG/RFUG for planting - although Tom Barr says it
can be done - I did set a tank RFUG with plants some months ago as a test.
That is too young to say what the long-term effect will be, but to date it
is problem-free set with very easy plants (Val and a variety of crypts).  I
only have to remember that unlike my other tanks, this one is water column
supplement only.

BTW, Penguin makes a matched powerhead series with available RFUG kits to
make such a setup OTS rather than DIY, much easier.