[Support request] Brown slimy matter in water tank

Hi josh
I have a 8 pot setup with a 100 ltr flexy tank.
It’s the first time I’m using it and it has been up and running for about 10 days.
I added the correct nutrients mixed in water before adding it all to the tank and have noticed that in the last few days the water has a brownish slimy film on top. I have added a water pump to try and mix it all up. It’s the same in all of the 8 float chambers. Any idea how I can solve it please? Do I need to flush the tank and the lines out and start again?
Thanks in advance
Enrico