Biowheel

That is a very small sump. One thing you want to make sure of is that your sump can hold enough water so that if the pumps shut off, your sump doesn't overflow.

 

I also have a 10 gallon refugium so there should be enough room in it to handle a power outage. Gravity will bring the water from the DT to the refugium and fill them both up.

 

yep, just make sure there's room

 

I will do a test and see what happens and make adjustments.

 

As for a skimmer, the conventional wisdom is to go up a size, or go as big as you can. If you have a 90 gallon, get one rated for a 120/150/180 size tank. If you get a skimmer that can't keep up with your bio load, it will be skimming 24/7, fill up the skimmer cup and require more maint on your part to keep it running at its peak. They loose efficiency as the organics that are skimmed out tend to build up on the equip.