Mildew/green scum in waterer

I have a 1 gallon auto waterer and the bottle is developing green scum inside. How do I clean it out? It has a 2 inch screw on top. Will bleach remove it or is that dangerous to my quail? Any tips from experience?

Apple cider vinegar can make it sterile while benefiting the animals..also painting it black will stop algae from growing as it needs light to survive..if it can be taken apart and cleaned with vinegar first then later using cider vinegar every so often to keep it clean.

Keeping it out of sun will help. I've had no adverse effects with it in my chicken and turkey waterers.

When i do clean it, a sponge gets it easy. No chemicals needed.

I second the apple cider vinegar to help keep things from growing in waterers. I generally use about a tablespoon to a gallon of water. As for cleaning, a bottle brush works great.