Yellowing on rocks?

Question
Hi,
  I have just started a freshwater tank about three weeks ago. we have only two fish in it right now until we get the hang of taking care of it as we are new to fish care. I have been watching it closely and just today I have noticed that some of the gravel on the bottom of the tank is getting a yellow algae like stuff on it. It is also on the large shell that we have in there. it is not on all of the rocks just mainly around the shell. when I picked it up I am able to scratch it off, and it wipes off easily off of the glass decoration. I have never heard of anything being yellow, if it were green I would think just algae, do you know what it is? and the best way to get it off. I got the tank from my uncle who had it running fine for some time, so I did not buy anything. I have checked my Ph and ammonia and they are normal.
  I appreciate and help and advice. Thank you and God Bless! -Elizabeth  <><

Answer
Hi Elizabeth

This is algae. There is both green and brown algae. Brown algae is actually more common in aquariums than green. Brown algae appears yellow when it first starts, then gets darker as it progresses. The best way to clean it is with an algae scrubber or an old toothbrush.

When I do my weekly water changes, if I have algae in the tank, I take the decorations out and clean them in the tank water I siphon out. Never clean them with tap water. It may also begin appearing on the glass, for this, using an aquarium scrubber will take care of it. These are available at your local fish store.

Hope this helps, good luck!

Richard