I have a gallon of cyser fermented with RC-212 yeast. This morning, I noticed there was a small amount of white gunk floating on the surface (around the edges) with a couple of strings reaching down into the cyser.

Uh-oh, infection, I thought. I quickly dissolved 1/8 tsp pot meta in some water, added it to the cyser, and stirred.

Should I add more? Will I be able in the future to make this cyser sparkling? It's already fermented dry to a SG of 0.998, and in fact I was planning on bottling it this week (I've already bottled the other two gallons).

My recipe, roughly:
just under 1 gallon sweet apple cider
700 grams honey
RC-212 yeast
1/4 tsp pectic enzyme (added during fermentation)
and now 1/8 tsp pot meta in 2 tbsp boiled water