Macroalgae (especially chaeto) is very safe, but caution should be used with vodka. European reefers are reporting that you can have problems including tank wipe-out by not going gradually enough and/or using too much vodka (causes bacteria blooms in such high concentrations that they can deplete the oxygen levels enough to kill fish and corals).
I am currently using 2ml of vodka on my 75g tank, and I worked up to that amount over a 2 month time period. I would prefer having a larger fuge to grow more chaeto, but don't have the room in my office for a larger sump.