You know you could always add some inexpensive base rock which then will become live rock from the rock you have. Many people put half live and half base rock in their tanks to boost the amount of rock. If your existing live rock is that loaded with bio then adding the base rock should be no problem. Just make sure the rock is suitable for saltwater and away you go. Sand for the bottom doesn't necessarily have to be live aragonite, you can possibly pick up aragonite play sand cheaper and seed it with live sand also. These things will help defray the initial high set up costs. A protein skimmer is important as eels do produce heavy bioloads.........much more than small fish do. Remember read read read and when you think you know something....head back to the books and read some more. This is a learning process believe me.