saltwater tank algae problem?

Sounds like either cyano or diatoms.

If your ammonia and nitrite is reading 0 your cycle is complete.

Do note that Cyano, diatoms, and macro/micro algae need nutrients to grow (phosphates and nitrates) If you keep the nutrients out of the tank (via regular water changes) the algae will go away on it's own. It'll take time, I had diatoms in my one setup for a couple months.. while in the other only a week. Even under perfect conditions, It is perfectly normal to get an algae bloom at the beginning of a setup after the cycle, but you need to "starve" it in order to get rid of it.. all those nutrients built up from the cycle feed it.. so stop suppyling them with nutrients, and keep your water quality up to scratch. Infact if you test your water for phosphates+nitrates.. you may get a reading of 0 because the algae soaked it up.

Whats your water source? NEVER EVER use tap, filtered, or any kind of water that isn't Distilled or from a Reverse Osmosis unit. Not only will it contain harmful heavy metals, bacteria, and other crap that conditioners won't take out harming your fish and invertebrates.. it will also have phosphates and nitrates for algae to grow.

Cyano you can peel off anything and even pick up off the sandbed like a carpet, while diatoms you can scrap off with a credit card (don't use a razor blade.. there is a slim risk of scratching glass).

1. brown algae is normal, do not do anything about it

2. your tank needs to cycle for 6 weeks or more, so you're about halfway

3. again, this type of algae is normal at this stage, do not do anything "to take care of it"