I'm not a fan of UGF's for any tanks, but here is why I believe they
are especially
ill-suited for planted tanks.

1) Substrate is very important for plants, not only does it serve to
keep them "rooted" it
also must provide nutrients to plant roots. UGF's limit the size and
type of substrate
materials that can be used. For example, one of my favorite
substrates is sand mixed with
iron rich laterite. It can't be used with a UGF plate because of
particle size, and laterite
would be introduced into the water column.

2) UGF's begin to become mechanical filters, as debris enters into
the "cracks" between
the gravel the biological filtration gets compromised and anaerobic
areas develop which
can kill plant roots and/or cause stem rot. Vacuuming is not
recommended because it
disturbs the plant roots, this causes the roots to develop more root
hairs which take more
energy from developing leaf structures. This is why it is often said
the UGF's will grow
great roots, just not great plants.

3) This is the main reason. For a real balanced planted tank the
aquarist needs to be able
to control nutrients, both in the substrate and in the water column.
A UGF will make it
virtually impossible to do this over any extended period of time.
For example, if I need to
add fertilizer tabs to sword plants, I push them deep into the
substrate not fearing that
they will be released into the water column. With a UGF and it's
associated water flow
through the substrate that fertilizer will be dissolving quickly
into the water column and
algae will be soon to follow.

4) What benefit does a UGF offer in a planted tank? NONE. Biological
filtration? Nope
the plants do this better. Chemical filtration? Nope, UGF's do none,
but plants are very
efficient at chemical filtration. Mechanical filtration? Nope, again
as I alluded to earlier,
UGF's begin to fail at the only job they're capable of if they begin
to provide mechanical
filtration.

So the question to me seems, if a UGF provides no benefit for a
planted tank, but offers
several negatives why would someone choose to use them.

BTW, up until about 7-8 years ago, every tank I have or have ever
had, contained a UGF.
When I was finally convinced to fore-go UGF's I found that live
plants became much
easier and that algae rarely is a problem,....and there is never
that foam at filter exits that
indicate the heavy DOC buildup that occurs with tanks using UGF's.

JMHO,

--
Steve H.

Yesterday is History, Tomorrow is a Mystery
But Today is a Gift...That's why we call it the Present!