The brown algae that you are seeing is called diatoms. It's part of the cycling process. Are you testing your water for ammonia and nitrite? If you don't want to keep cycling constantly, go ahead and buy about 20 more pounds of live rock and 30 pounds of base rock. The base rock is much cheaper then live rock, and you shouldn't use more than 50% base rock in a tank. Once you get the rest of your live rock and base rock, throw in a small piece of shrimp, like the shrimp tail with a little meat in it to kick start your cycle. The cycle begins with an ammonia spike, which bacteria eats up and turns into nitrite. Nitrite is still harmful to fish, so another bacteria eats it and converts it into nitrate. Your initial cycle is done when ammonia and nitrite read zero. Once your tank is completely cycled, you can add one fish. A cycle takes anywhere from one week to 30 days to complete.
Don't worry, you're on the right track! seeing diatoms is a good thing. They will go away with time. Eventually, green algae will start to grow. It's just part of the cycle.
Here's a few tips for you...
1. do not top your tank off with saltwater. Only use Freshwater for top offs.
2. All top off water should be RO/DI water... purified... so that excess nitrates and phosphates do not enter your tank.
3. Buy an accurate hydrometer or better yet, a refractometer to know your specific gravity (salt content of your water)
4. Buy the basic API test kit. Ammonia, Nitrite, Nitrate and pH.
5. Figure out what you want to keep and then decide on the equipment that you will use to keep the livestock that you want.
6. Research everything before you buy, this includes equipment and livestock.
7. Not all equipment is equal. Sometimes it pays to go ahead and buy the best equipment you can afford, instead of buying cheap and realizing later that it needs to be upgraded.
8. review the 101 tips for new hobbyists in the new hobbyist section of the forums.
Never stop researching!
