Plumbing, A few new Questions

[spoot]

Not sure how the herbie works (haven't read up on it) But by the picture, it looks as though the overflow pipe for the herbie is only halfway up the tank. How high will it be in real life? If it is this low, you will have a lot of water draining into sump in the event of a power outage.

From the looks of your diagram, what you should do is just drill a hole in the sump for the skimmer pump. Then drill a hole in the refuge for the skimmer output. That would solve your problem.