SW - Water Change - Need Help

[TVR]

Hi All:
My tank had been up and running for a few months now (3-4 months tobe exactly) and haven't got any water change yet as I tried to follow what people mentioned about fully cycled. Now I wonder, should I atart soe water change sicne I start seeing some bad ageas (Like green hair, brownish...).
Any idea? - How about the Skimmer,when should it start being plugged in?

Thanks Guy