Eclipse filters clogging up very rapidly...

I have a Eclipse 25-gallon tank with two blackfin tetras, about six or
seven danios, and an 8" pleco. No plants other than plastic ones, and a
big piece of driftwood. I had previous algae problems a few months ago,
but they haven't recurred.

Still, the Eclipse filter cartridges clog up *very* rapidly, on the
order of a week or two until the water's going over the spillway to the
bio-wheel rather than through the filter. They clog up with a green,
sludge-like mass.

Almost no food flakes are reaching the inlet, as the fish gobble them up
rapidly. Occasional strings of pleco-poop are floating around, but
settle down to the rocks within a few hours. Presumably they get run
through the filter, but I never see them (maybe chopped up by the
impeller?), nor do they appear when I do water changes.

The water is crystal clear, with no floating algae, debris, or other
issues. Chemistry is well within normal limits.

Yet these filters clog up within a week or two, when I've been told
they're rated for about a month. Certainly not a mere week.

I don't really mind changing them that much, as they're not that
expensive, but this has been going on for at least two months, and I
figured that there might be something amiss.

Any ideas?

--
Pete Stephenson
HeyPete.com