Barliman
Aquarium Advice Addict
What is the original purpose of excel? Is it harmful to fish/plants?
It's a liquid source of carbon for plants. Not as effective as CO2, but still pretty good. In fact, I'm having very good results with it.
It has a side benefit of killing many forms of algae. I was inadvertently overdosing it and thus had *no* algae problem. Luckily I didn't harm my plants or fish, either.