Yes, that's exactly right as far as the water getting removed while you're doing the vacuuming. Regular tap water should be fine unless you have really delicate species. Most people just put the chemicals in, then add the tap water (at the same temp as what's already in the tank). The clear water clarifier isn't necessary, and you shouldn't add ick cure on a regular basis, only if you actually have ick. Even then, most of us recommend the heat/salt method instead of chemicals. I would also recommend investing in some Prime water conditioner, it seems to be the best one out there. Another thing you can do is test your tap water for ammonia, nitrite and nitrate. If your tap has any of those in it, you might want to let it sit for a day or 2 before putting it in the tank. That's what I do cause my tap water has ammonia in it. If it doesn't, you can probably just put the conditioner and the water in at the same time, just make sure you add enough to treat the whole tank, not just what you're adding.