100% is always nice, but not really necessary for a tank that small. You should maybe consider it for the long run? Buy a bag do half half and maybe save the other half of flourite for another future tank. I dont' think there is much of a big difference between 50/50 compared to the 100% when you're dealing with a 10 gallon tank. Budget and use your resources wisely. I'm sure you'll be happy to know you have some extra flourite when you need it the most.