I have a 50 gallon container I keep my pretreated/heated water in which I dose with Prime. I last refilled the container a few days ago and when I went to do a water change today I couldn't for the life of me remember if I put Prime in the water. Seachem and other sources says it's "completely safe" to double dose Prime's prescribed 5mL for 50 gallons so I went ahead and gave my 50 gallons another dose. Better safe than sorry, thanks Alzheimers.