I have used the magnesium method (Tech-M) and turbo snails, both separately and together. I never lost any inverts when dosing Tech-M, but I did it very slowly. I have also used relatively large turbo snails (my tanks are nanos), and they also did a good job, and they are currently my favorite herbivore (except they do not eat bubble algae).
In a tank your size you will have a greater choice of herbivores of course!