If you want the fry to live you are going to have to move those two to another tank, specially prepared for them because when tiger barbs lay their eggs they actually scatter them around the tank and sometimes afterwards go down to the gravel and eat them!
I'm pretty sure your tiger barbs are preganent because the feamles are normally the more plumper and rounder ones.
When setting up the specially prepared tank you should have two layers of marbles on the floor so that when they do scatter the eggs, the eggs would fall between the marbles out of the reach of the hungry parents. After the eggs have been layed/scattered take out the females and wait for the eggs to hatch.
To make sure the tiger barbs are preganent some people have a group of tiger barbs in a specially prepared breeding tank and just wait for them to breed and spawn.
As you can see this is a kind of hard job to do but if you are willing to breed your tiger barbs I won't stop you!
Good Luck!
