Change the water as best you can. Use a net or floss or something to avoid the fry. As close to same temp as possible ( a couple degrees). Wrap the tank in white paper. Leave a night light on in the room. You're getting the parents to be dark shadows to attract the fry. No guarantee, but a technique that might work somewhat. As parents get more experienced, I think they do more to herd the fry. It might just work out better next time around.