Got to agree with Chris(Crumbs) here. Nothing Cool about it. From the looks of the photos - that Nurse shark is over 24" long. So keeping in a 300 gallon tank with large Morays, and another 4' fish, as well as another Nurse shark - is a horrible idea. In fact it's down right cruel.
At 2' long - the Nurse sharks should have a tank/pond that is at least 50 sq.ft. and 750 gallons to live in for just another year - and that's the bare minimum. They would really be better off with a pond that has a footprint of more than 150 sq.ft and a volume of over 3,000 gallons so they wouldn't to upgrade to a larger tank for another 3-4 years. But either way they will need a tank/pond with a footprint of over 700 sq,ft and a volume of more than 21,000 gallons to live in for their entire life.