Let me try to answer all the questions
This tank hasn't been moved, it's been running for years. We just moved into the house where it was running. It had been running with sand and live rock only for several months (they used to have fish etc).
After learning that low-flow can cause the Cyanobacteria, I went out and bought my first powerhead. It's a koralia at 750. I'm planning on buying a second one next week to get the flow where it needs to be.