I have been using Irish Moss (along with yeast nutrient), added at 15 minutes before the end of the boil. When I started using it, it seemed to help. For me, there is a side benefit to my brewing process - I'm never late for the 10 minute hop addition. In most of my recipes, there is a 30 - 45 minute gap between start of boil and the 1st kettle addition (at 15 minutes) so I'm often off doing other things. Starting with the 15 minute addition, I stay close to the kettle so that the 10, 5, and flame-out additions are added 'on time'.
A rather unusual way to brew a gallon batch. Pitching at 80* is that typographical error that's apparently still in the five gallon kit recipes (like @hd4mark said, mid 60s is better).
I'm going to guess that you pitched around 2 grams of yeast (saving the other 4/5 of the package for the rest of the batch). If so, the rehydrating the yeast seems reasonable when working in relatively "uncharted" territory (brewing 1/5 of a five gallon batch).
Some additional thoughts on yeast in smaller batches:
- It's reasonable that the simplest (and safest) thing to do is start with a fresh package of yeast, pitch around 1/2 of it, and discard the rest. Only the outside of the outside of the package and the scissors need to be sanitized.
- It's also true that people post about pitching 2 grams of yeast into one gallon batches. And yeast calculators will confirm that this is a correct amount to pitch. (Let's leave open the possibility that there may be other 'correct' amounts to pitch ).
- With gallon batches, my personal experience with fermentation temperatures in the 65* range (+/- ~2*) is that I can pitch either 1/4 package or 1/2 package, either dry or rehydrated, and get the same result.
- I'm back to pitching 1/2 packages dry (for a while anyway ). Open packages get used with 4 - 6 weeks of being opened.
- In your recipe notes, it may be helpful to track if you used the 1st half of the yeast package or the 2nd half of the yeast package.