1. pull the water going into the skimmer directly from the display if it isn't already. By doing that you will be removing more free floating algae "spores" as well as diatoms.
2. add UV
sterilization, that would also help prevent the spreading by killing any free floating in the water.
I recently switched from a 30 to a 50 and added 20+ pounds of new substrate and had the expected diatom bloom like crazy. Within 3 days of adding UV
(15 watts @ <100gph) that was using water being pulled directly from the display, it has disappeared and all other forms of algae are greatly reduced in how rapidly they are propagating.
not certain if it's a direct effect, but I can't think of any other reason for the change.