Tyga now wants to use Blac Chyna's drug arrest against her in their custody battle

Tyga is alarmed his baby mama was
arrested for possessing ecstasy and being
wasted in public, and he's now sharpening
the legal knives to wrestle custody from
her.
Sources connected with Tyga tell TMZ he's
alarmed at Blac Chyna's arrest in Austin
last week, and is worried her problems with
drugs and alcohol might be putting 3-year-
old King at risk.
Tyga has already filed legal docs to change
the custody arrangement, and now thinks
Chyna's recent run-in proves he's the more
responsible parent and he should have King
during the week, allowing her visitation on
weekends.
And this is interesting ... we're told Tyga is
well aware of the video Rob Kardashian
posted of him playing with King. We're told
Tyga is cool with Rob's relationship with
Chyna and has no fear about being replaced
as a father by anyone, including Rob.
Tyga thinks Rob is a good guy and has no
problem with him. Chyna on the other hand
...