I have a 18 gallon high that I have been running for over a year (converted from a 10 gallon before that). The system has a 5 gallon sump and I use a 250W DE halide for lighting. I have been keeping SPS/clams since it was established and it has been going well. I have to agree though that it definately very hard to keep stable, and sometimes your coral color or growth will reflect this. But who doesn't like a challenge
