Refugium and foam

[bonniewoodruff]

I have a hang on the back refugium on the back of my 65 gallon FOWLR. I keep the light on 24/7 and have for the last 3 months. When cleaning the tank last week I noticed there was a lot of white foam on top of the water and when I went to remove it, it was hard on the top and a pink slime on the bottom. Today I notice the foam is returning. Does anyone know what it is? Do I need to do something about it? This is my first refugium.
Thanks for your help.

 

[bonniewoodruff]

Here are pics

 

[Terrance]

Do you run a protein skimmer?

 

[bonniewoodruff]

Yes, it is built in.