Ok. Well, if your fry are in good continuous current make sure they have somewhere to hide and sleep. They can exhaust themselves swimming continuously if they don't have 'still areas' to rest in.
Making a fry divider:
Plastic mesh- Can be found at a craft store or craft department in paper sized rectangles. It's flexible but not floppy, and there are a few sizes- get one that looks like the holes are big enough for fry to swim through but not bigger guppies. You may also find a mesh fine enough at a garden supply store, but you might end up having to buy a whole roll.
Slide dividers- Go to a office supply store or department, look for presentation covers- you're really looking for the binding but most come in packs with plastic sheets. You want a straight slide binding that looks like this
http://www.gmstationery.com.au/images/S ... inders.jpg
I don't know how to put in links, but this should lead to a picture they're hard to describe.
Cut the plastic mesh to the size of the tank, place binders on each side. This keeps it straight and allows you to anchor it better, and helps keep fish from sneaking through at the sides. If you have substrate, bury the bottom in the substrate and maybe place decorations or suction cups at the sides to help it stay in place. You should be able to make it snug, but if you have a strong current it might fall over. If you want to make it permanent you can use aquarium glue on the binders.
Make sure that you have plenty of places for the fry to hide on the side you want them to stay on. They will be able to pass through, but it keeps the adults contained. Also the mesh design allows for excellent water flow through the divider so both sides of the tank can stay healthy.
Good luck!