It's a bit iffy on how often to change the mixture, I've never had it on an aquarium bigger than 55 gallons. Normally, a mixture will last about 4-5 days. Often times on bigger aquariums, you would need a few other co2
setups to accommodate the size. You might check with someone that has more recent knowledge because it's been a few years since I've had my own co2
It's worth it though! I was thinking of using a 5 gallon bucket this time around so that I don't have to have so many bottles around- but i have to research it more and see if it's doable.