Cory
Excel isn’t exactly co2 in my opinion,it’s watered down glutaraldehyde which isn’t the safest of chemicals, it’s mainly to kill off algae and it does that by mutating the algae beyond the ability to grow any further, so with the algae mutated it’s no longer taking up nutrients and allows the plants to do so. I have a gallon of the actual chemical that you are welcome to,just have to water it down to half strength to dose the same as Excel. Sooo long answer short I’d go with the co2 tank