If you stick to the basics in keeping Opae I think it's extremely easy. Basics meaning the following:
1. Lava rocks only. No substrate i.e. sand
2. No feeding. If you do feed only at the begining in order to get the tank going. Since the waste from the Opae feeds the algae you do need to get that going. If you feed use freeze dried spirulina.
3. Keep your temperature constant. Not too much fluctuation.
This is pretty basic. This is an exact example of my jars. Lava rock, no substrate, no feeding, and they are breeding. At one point in time I did feed my tanks once a week. I do not at all anymore. Temperatures in the summer does fluctuate too much and gets into the upper 80 degrees which seems too high for the Opae to breed. Winter time the temps are in the mid to lower 70's. Keep it simple.