One of the live rocks has grown a lot of red and purple algae.  This is partly expected – algae likes light just like coral does.  It must be feeling right at home with the new lighting we got a few weeks ago.  At fist I was thinking this was pink and purple Coraline algae, which is expected on live rock, but now I’m beginning to wonder…

Live rock with red and purple algae

The red algae has now migrated from the one live rock, to some small pebbles and a few empty shells in the tank.  I even found it growing on some substrate the other day.  In the picture above, you can also see a little bit of green hair like algae on top of the rock.  It hasn’t attached itself to the glass yet, except for a little bit in the back glass.  I’m trying to get the rear glass covered naturally anyway, so I’m not really concerned about that as much.

So, what to do?

I like the colors on the live rock.  I don’t mind it growing there, as long as it doesn’t spread too much.  So, I need to find a way to keep the algae in check.  A couple of things to do:

• Algae survive on nitrates.  I need to keep my nitrate levels reasonably low
• Hire a cleaning crew

I check the water chemicals once a week.  The last few weeks, the all the levels have been reasonable.  Ammonia and nitrite levels have both been zero.  Nitrate has been between 5 and 10.  I do a 10% water change weekly if needed.  Even though it doesn’t seem to need it, I’ve changed the water anyway for the last two weeks.

So, that leaves one option – hire a cleaning crew.  The Geothermal Aquaculture Research Foundation (GARF) sells what they call “Reef Janitors” for what seems like a reasonable price.  Reef Janitors are Hermit Crabs and algae eating snails.  Apparently these guys will make short work of even the worst algae outbreaks.  For a 50 gallon reef tank they recommend over 80 Reef Janitors – that seems like overkill to me.  I think I’ll start with somewhere around 20 or 30, and see how it goes.