Ok, half teaspoon every other day probably isn't causing the water to bloom, and I do apologize if I got too...'aggressive'...but as you hang out here more, you'll see a lot of novice who are either given bad advice, or get duped into believing in some 'miracle product'...which does more harm than good.
Good example - algae destroyers....most of these do kill the algae, but contain ingredients that'll spawn another algae bloom in a short time. Another good one is 'perfect pH' and other pH adjusters. Most of us don't keep fish delicate enough to worry about a specific pH to maintain...and those that do use more reliable/natural methods to correct pH issues (like R/O water, peat, crushed coral, calcium carbonate...etc)
The white stuff on the log shouldn't be a problem, but if you follow my boiling instructions, it might keep it from coming back.