I would tape the bottom also, can make it wider. the point being leaves you with a clean feathered edge, no ruff spots or build up to become a particle hang up. just be sure to pull the tape as soon as possible, not like painting, you want to pull the tape while the silicone is still fresh and uncured. let any silicone that got on the sides of the tank or bottom cure and then remove with a razer blade later, other wise it just makes a mess.
