That would work but if your fish ever needed to be medicated, you risk contaminating the reef tank. The only safe way is to have a completely separate tank. Its funny.... when hobbyists have everything (their reef tank) settled, they look for a new challenge (Im as susceptible as the next guy). At one theme I had over 16 tanks for a total of about 1500 gallons of water. I would do a separate fish only tank. If you do get another tank I'd recommend at least a 55. I wouldn't go with anything smaller