I truly can’t thank you all enough. For 7 seasons I’ve maintained and held a very well balanced pool and never needed to really ever add anything other than some balance pack to raise alkalinity once or twice a season. And of course the liquid shock after a pool party or heavy rain. And some just for weekly chlorine. Last summer I stopped adding algaecide weekly. I felt with a bal. Pool and good FC level it was just another chemical I didn’t want in the pool. Maybe I shouldn’t have stopped using it ??? Also when I closed the pool, I opted to not use the winter shock. Instead I put 2 gal of liquid shock in the week before closing to super shock and then bal. the PH, Alk. And added winter algaecide.Once the ammonia is deactivated , your chlorine can finally get to work to kill off the algae. You'll hopefully need another 8 gallons, but you'll never know. It's better to have too much on hand than not enough. Eventually, you'll use it.
Don't be sorry. We've all been there. It's a continuous learning curve. You're doing great!