I'm facing the same problem.
I would say that because the fry do not depend on the parents for anything other than protection that they could be removed when ever you wanted to. However, I do not know the long term effects if any that this would have. I have read some reports that with certian species of fish, that when the fry are removed too early that they do not learn some behaviour from the parents. Unfortuneatly I do not remember the species in question, and do not know if this aspect would affect krib fry or not. I seem to want to say that it was reguarding some species of shellies and the youngs willingness to take to shells. Back on subject, sorry...
So when ever you want to remove them should be fine. Also I think that the less fry that are around, the more your pair will spawn. Be warrned however that you do not want them to spawn too much because it will put much undue stress on both the pair after a while. I would leave some fry to stay with the parents to help keep any agression down.
How you want to move them depends on how big they are. If they are small enough to syphon out with airline tubing that would be a great way to move them. If not, mabey try a little larger tubing. After that, the only other real option is to grab a net.