There is no good reason to ever dose 5 ml per 10 gallons, even though Seachem recommends it. Excel breaks down in the aquarium within about a day anyway, so you might as well just dose your regular daily dosage from day one. Doing the Seachem recommended first day dosage is a pretty sure way to destroy your vals, and other sensitive plants, without gaining anything by doing so.The initial dose of 5x is only after a large water change. You can dose 2-3x safely to kill algae. If you dose 5X on a normal basis, you may suffocate your livestock. Seachem addresses this in their FAQ, and it's a pretty common topic. A google search will do wonders.