Hmmm Skimmer question.

[Stretch]

Well I would go by the size of the main tank, the sump is just water, a fuge has water plus macro algea, which really won't add to the bio load, the entire systems bio load is contained in the main tank. Thats just my reasoning anyways.

For my system my 75g tank 20 sump 15 fuge, The sump isn't quite full so i probably have a total of 107g's of water.

I run the euroreef ES 6-1 which is rated for 100g I love it. THe whole reason i run it, is mainly because it's the only one that would fit in my stand/sump setup.