My Lovely Algae


Algae to an aquarist often mean trouble. It is one of the continuing ‘don’t wants’ of the aquarium. Hair algae, slime algae, yuk, no thanks! Then there’s the algae that’s purposely grown in a sump to aid filtration, usually Caulerpa.

The algae referred to here is none of the ‘horribles’, or Caulerpa, but the ‘reefy’ encrusting algae that is welcome, by me anyway.

At first when the aquarium started I used to keep all four side glasses clean. A considerable time later I noticed that encrusting algae had taken hold in a back corner. A closer look showed that it seemed decorative and welcome, so the algae’s impending doom with a scraper was averted. One end of the aquarium was not cleaned at all; it was left to its own devices. The glass turned green, the usual stuff, but despite twitching with the urge to clean it off, it was left alone. Over a few weeks it gradually turned dark.

I thought about this for a while, and then increased the alkalinity of the seawater from 2.5 meq/L to 4.0 meq/L. The reason for this action was that it had been anecdotally reported that bad algae grew poorly with higher alkalinity, but encrusting decorative algae does better. Having done this I monitored the corals carefully but nothing untoward occurred.

As time progressed the glass that had been left turned into dark, medium and light green patches. It also developed lots of tiny white pimples on it. It looked great.

Having obtained reassurance by this ‘experiment’, I left the back glass alone and just kept the front and one end glass clean. This was probably going to happen anyway as the corals were larger and getting to some areas of the glass had become difficult. The algae continued to develop and then covered the stated glass panels completely. The aquarium looks really great with this natural decoration in place. The original blue of the back glass can no longer be seen.

The alkalinity level has been maintained at 4.0 meq/L for years and the encrusting algae do seem to appreciate it.

I did note that algae over an area of about 2 square inches had come away from the glass and fallen down; it could be seen on a rock. The glass where it had been was clean. The fallen alga was quite thick, about 1/8 of an inch, so I assumed it had simply lost adhesion, glass is hard and smooth. Sure enough, the clean area was soon being taken over and is now once again covered.

Something else I have noted is that tiny shrimps, similar to the ones that scurry over the rocks and sand at night, take refuge behind some areas of the algae. Close inspection shows that the algae appears to be slightly loose in place – I wonder if the beasties have burrowed their way in or simply taken advantage.

Over time one or two additional patches of encrusting algae have come away and are growing back. Taking a photograph of the algae is difficult as corals tend to get in the way, however I did find one area that is reasonably open and used that. The patches on the left can be seen, in process of re-covering. Original algae can also be seen. Incidentally, the attached ‘leafy’ algae that can also be seen aren’t what I’m talking about, but are also very decorative. It is also very friendly in that if any does grow where it isn’t wanted the whole ‘leaf’ easily comes away for removal.

Algae can be the aquarist’s friend, adding a natural decorative background and increasing the overall attractiveness of the aquarium.

  1. Nice picture of the Encrusting Coraline Algae. It’s also curious that you have little shrimps running about. Have you tried to ID them?

    Saltwater Fish Tanks last blog post..Saltwater Aquarium Temps for Metric

  2. There’s loads of the little beasties particularly at night. There’s a fairly large population that lives around the small rocks on the DSB. They are pretty common appearing in many reef aquariums. I haven’t tried to identify them properly, though I did have a quick scan once at my reference books and failed.

    Johns last blog post..The Banggai Cardinal At Risk?

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