For what it is worth, and this is meant as an anecdotal example, I use Excel as my only carbon source on a 20-long with a 65W power compact (Aqualight). I first started using as per directions on the bottle, which meant 2ml of Excel per day. I now use 6ml per day. Fish{1}, plants and inverts{2} seem fine. I dose KNO3, KH2PO4 and CSM+B as per the "EI Light" article, with a 50% water change every week.

-Jason


{1} Fish: 3 male panda guppies, 1 otocinclus, 3 dwarf puffers, 6 pygmy cories.
{2} Inverts: 3+ asolene spixi snails