Hi all, I'm one of the occasional lurkers - it helps me maintain my pond
scum aquarium for winter microscopy. Thanks for all the help. =)

Anyway, here's my obligatory wierd question - if I wanted to go to the
local lake, and hang a hose down into the water and pump small quantities
though a filter paper and back into the lake for ten minutes or so... are
there small pumps that could pump water like this up against a filter (high
resistance, should probably be considered 'clogged')?

I guess such a pump would have to somehow avoid building up a lot of
pressure, maybe let water slip back though to avoid popping the filter
paper? Being able to adjust the pressure it produces would be ideal. And
it needs to not "chop up" the water - so obviously I am way out of my league
here.

When I do this in the lab, the filter only lets though about 100ml a
minute. It's a 4" circle of paper, supported on a surface full of holes at
the bottom of a fancy ceramic funnel, and vacuum pulls the water through.
After awhile, the paper turns green, and holds lots of nifty little
microscopic life - of the open-water variety.

I can build the filter bit, but need suggestions as to pump technology.
Are there little fountain pumps like this, for example? Any help
appreciated! -cmb

p.s. - Happy Thanksgiving!


I am also a lurker and extremely rare poster. I am assuming that you are a
biology teacher, as am I.

Anyway, what immediately came to my mind (and because it was immediate may mean
it is not workable) is to use just what you suggested, a fountain pump, or
perhaps the very small Fluval. You could partially obstruct the aperture to
achiehe the flow you want, or collect your flora on the inflow end on a filter
medium of your choosing.

Powering the filter at the lake would be the portability issue. Were you
planning on using a power inverter? Does anyone know if there would be a
safety issue with this? Certainly electrical cords around an unpredictable
water source like a like would be cause for concern.