Fry are very delicate so if I were you I would use water from your main tank in a 5G and simply put in a small filter (or powerhead) with a sponge on the intake to make sure you don't suck up any fry. It won't require anything powerful.
Also I would buy a cheap small filter and put the media in your main tanks filter for a week or two to mature, then put the filter in your fry tank once they are a little bigger.
Just be sure not to overfeed the fry or your tank will get polluted, maybe hatch some baby brine shrimp and use that as food. Although for the first few days they probably won't require any. And crush up the flake food of course.
I am no expert on the subject but this is what I have done in the past, never failed.
Tom
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