Getting rid of copepods

Some time ago I bought a really nice, big Jade Sword plant for about
$20. Soon after putting it in my tank, the leaves all died, and it
looked like the whole plant was a lost cause.

Since I'd paid $20 for it, I decided to experiment. I put what
remained of the plant in a one gallon container, with a layer of
regular potting soil covered by a layer of gravel. I carefully filled
the container with water and put it in the window sill where it gets
full sunlight part of the day.

After about two weeks it's actually starting to recover, with a number
of small but healthy looking new leaves. However, there are also lots
and lots of little critters, perhaps a half-millimeter in size,
zipping all over in the container. I believe they're copepods, which
would not normally concern me, but they're clearly reproducing out of
control since there is nothing to eat them, and they're unsightly.

So, I'm looking for ways to get rid of them. Ideally, some small
critter or fish that could cope with the conditions of this 'tank' -
about a half gallon of free swimming space, one struggling plant, mild
temperature fluctuations during direct sunlight.

So, what critters eat copepods? I could try putting in a single
peacock gudgeon I suppose.

Worst case, I'm willing to use chemicals but I'd prefer not to.

Any suggestions appreciated.



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