With a sedra 3500, that should be fine for up to about 110 gallons, check out a G2 on
www.asmskimmer.com
I would get a bigger skimmer than that though, in case you want to upgrade to a larger tank in the future, or hook in more than one tank to a common sump. Ask him to upgrade to a sedra 5000 at least, the G3 is ASM's most popular model good up to 180g. Plus I don't think you can over-skim.
What is going to feed the skimmer water, the drain line from the tank, or another pump?