Don't do a 100% water change right before you take off.. especially on an established tank with a cycle already. You run the risk of your tank crashing and restarting a cycle, which in turn can cause deadly spikes that you won't be home to catch and do a water change for. So doing a 100% on established tanks, is a dangerous idea.
As mentioned above, some snails (such as nerite) love certain algae, as well as ghost shrimps. I would personally go for the shrimp, as they have very small bio loads unlike snails, so it won't be a shock to the system adding in new tank mates.
How long do you keep your tank lights on? It will depend on what type of plants you have, but usually an 8-10 hour session a day is all that is needed.