Lots of bacteria growing and dieing?I have also been perplexed on how I can get algae in my coral frag/grow out tanks when they are fishless, I don't feed it, and my PO4 read <.02ppm.
Right, the corals need some nutrients to thrive.There will be misc leftover nutrients from rocks, plumbing, and pretty much anything.
If you just scrape algae, it dies, nutrients go in the water, algae then simply re-grows. You have not truly removed the nutrients.
You need to get nutrients to 0. Not easy. And not something you really want anyway once you add coral and such.