Day 22 float test on eggs. No movement 😔

Murtle the Silkie went broody on her own egg, so i put 2 other freshly laid eggs under her then another one 4 days later (it was warm). I've seen her off them 3 times (having a dust bath, scratch and poo), then she gets back on. We've had some cold nights and windy days here in Darwin (cold for us used to the hot humid weather). She likes to nest on the ground, so i put her in that cage to lock at night; incase of snakes. When do i open them up, to see if my rooster is fertile?