I wouldn't worry about Seachem GarlicGuard as the fat level from the garlic would be negligible, if even present at all in that product? Keep in mind that it's only the fat from terrestrial based plant matter that causes problems, and only if fed in excessive amounts. A little now and then won't be a problem, but as you say if a fish is already getting the same garlic compounds etc in a dry form, from a commercial food, then why bother with fresh? Finfish do best getting their fatty acids from marine sources, such as fish/krill/shrimp etc, not from soybeans, cottonseed, garlic, etc.