To free up space on my PC4s can I run my 2 mp40s on the same outlet?

If I add another PC4, behind my tank is only one outlet that's already plugged with my 2 other pc4s, how do I add the 3rd? Is it safe to add a power strip then plugg in the pc4s to it... Or one of those temporary GFCI boxes?

If I would have known what i know now, I would have added another outlet behind my tank before it was setup...