black fungus/algae

[hitz2b]

My mom's 5 gallon has a black fungus growing on the rocks and artificial plant. It just appeared within the last two months for the first time (she's had the tank for 5 years). No new fish have ever been added, just the original angel fish. She got new rocks, plant, and decoration after the first time and it still came back. Wondering if anybody knows what this is and how to get rid of it.
Thanks

 

[VoodooChild]

How long does it take to grow back?

 

[hitz2b]

it came back in about 3-4 weeks

 

[VoodooChild]

Just clean the tank. With an angel in something that small I'd be doing water changes every 5 days or preferably sooner. More than likely it's just a mold or a fungus. The nutrients probably have just reached a critical point. Try feeding every other day too.