It could be coralline algae, cyanobacteria, dinoflagellates, diatoms, red/brown algae...
It's algae and you're gonna see a lot more of it.
Most likely, this is due to organisms growing on the rock rather than being related to iron staining.
Really the biggest thing is time, patience, CUC and water changes. Starting with that dry rock, your tank needs time to develop it's biological filtration. Until that rock matures and you have corals or macro algae to absorb nutrients, you will have algae breakouts like that. It may seem to come in waves while you fine tune your tanks' export methods. For example, I had problems with algae so I started dosing nopox. Between the dosing, coral growth, and skimming, I stripped too many nutrients out and caused different problems and needed quit dosing nopox. The amount of nutrient import/export needed to keep that ugliness in check will need to be modified as you add fish, inverts, and coral. Especially once the coral starts growing.
This is film algae and in alignment with a maturing and cycling tank. Being tank is one month of age, you can reduce white intensity slightly and add a few snails such as:
No! Nothing needs to be dosed. You're throwing away money. All you need is a regular maintenance schedule including water changes, a good cuc, and patience
And a magnetic algae scraperNo! Nothing needs to be dosed. You're throwing away money. All you need is a regular maintenance schedule including water changes, a good cuc, and patience
