I really should know this, but

My 75 gal tank has been up for a month now. All the rock I made myself. I have a small frag plug with coraline on it. Just the other day my tank started getting brown algae on the sand and rocks. This is the dotom algae right? Just a step of the tank getting "older"?

The only light on the tank is a 14 watt LED blue & white light box. About one square foot. And that is where the algae is growing. Only one clownfish in tank and I used Dr. Tim's one and only.

 

Yes, sounds like diatoms. From what I have read, they need lighting so that may be the only spot you will see them. Unfortunately, with such a small amount of light, it may be quite some time before all of the silicates from your rock, sand, and equipment are used up. Best bet would be to get your permanent fixture(s) up and running to speed the process up IMO.

 

+1 get the bloom over with quickly