Razzo, really great looking comps and calvus! I ordered precisely the same zebras (from Ms) for my Tang setup and they do a fantastic job. Well done.
A note about diatoms, from personal experience. High silica levels are a significant factor. I fought diatoms and then decided to test silica levels (Seachem test kit) in my tap water. Ideal levels are below 1 unit. My tapwater is off the chart at 25+. I added RowaPhos chemical media to my filters (absorbs silicate as well) and problem solved. That said, snails >>> RowaPhos