I do not recommend Excel. First, it will melt some plants (Vallisneria is one, also mosses do not tend to like it much). If overdosed it can harm and even kill fish [a thread earlier today lamented over this unfortunate fact], and one member mentioned that it caused serious irritation on his hand. It is a chemical, and I question its effect on fish. Just a caution.
Thanks for the heads up Bryon. Don't wanna sound like I'm going against the grain here but I've been using Excel in my other tanks and it works wonders. I've spilled some on my hand and never had any irritation and I didn't notice any signs of stress from the fish when dosing, in fact the only time I've noticed stress from the fish is the first time I started up the Co2. I'm also aware of it melting Vals, mosses and possibly Wend. crypts. I don't use those plants for that purpose.
It keeps my algae to a minimal and plants seem to love it with the combination of Co2. I would never overdose as I measure using a syringe. But if I happen to lose any fish in the next month or so I'll stop usage so thanks for the heads up!