Fish Lab & Marine Aquaria

Clownfish Breeding

• Clark’s clownfish (Amphiprion clarkii) – we have had good success with our hatchlings, and now have 49 healthy juveniles in our display tank.
• Maldivian clownfish (Amphiprion nigripes) – several egg batches but no hatchlings this month. We have 12 juveniles ready for release onto the natural reef.
• Common clownfish (Amphirion oscellaris) – several egg batches but no hatchlings this month. Our 3 juveniles continue to grow.

We continue to maintain levels of Artemia to feed our Clownfish juveniles and inhabitants of the main aquarium. Rotifer production has been reduced, and we have performed deep cleaning on the equipment. During the global lock-down, we have been reviewing all of our operations and have implemented various changes to scale back and lower running costs:

• the water pump rate for our tanks has been reduced from 38mᶟ/hr to 20mᶟ/hr;
• breeding tanks #1-20 have been emptied, and our Clownfish rehoused in tanks #21-35;
• various marine specimens have been relocated to the large aquarium;
• we have drained our interactive touch tank and released the marine inhabitants;
• the sand filter back-wash procedure is now performed every other day;
• we are cross-training extra staff to keep things running smoothly.

Small Aquarium One

Increased water temperatures have increased the growth of algae and caused bleaching in the mini-frame Acropora coral fragments; 17 fragments have encrusted, 1 fragment is bleached, 7 fragments are dead. We have also transplanted a new mini coral frame (KH06) with Galaxea fascicularis coral fragments, which is doing well so far.

Small Aquarium Two

The mini coral frame has 19 fragments; most are now encrusting, but 12 are bleaching and 7 are paling.

The Clark’s anemonefish (Amphiprion clarkia) breeding pair have laid 3 egg clutches this month, and we continue to study egg development under the microscope.

One new addition is a partially-bleached colony of Acropora microphthalma that we rescued from the lagoon. We will monitor this colony and hopefully follow its recovery process. The coral also came with some hitch-hikers… three furry coral crabs! [photo]

Moon Jellyfish (Aurelia aurita)

Sadly, our Moon jellyfish have all fallen victim to the increased water temperatures and reduced water flow this month. We had previously seen that jellyfish are very sensitive to adverse environmental changes.

Our jelly fish polyps, however, have shown a marked improvement. We relocated the Kreisel tank into the Fish Lab to provide better air temperatures, and have increased the feed to 500ml of S-Presso enriched artemia (day 2). This has improved the number and condition of the polyps, with a healthy orange hue and widespread attachment.

Large Aquarium

The reduced water flow (to lower running costs) has affected our large marine aquarium. The resulting lower oxygen levels and seasonally warmer water temperatures have combined to prove fatal to many of our marine inhabitants. We have replaced some of the lost herbivores, but the resultant algal overgrowth will take some time to restabilise.

• Zebra dart goby (Ptereleotris zebra) – reach a size of 12cm. They are fast active fish, that stay close to their hiding spot for if they feel threatened by larger individuals.
• Yellow tail basslet (Pseudanthias evansi) – schooling fish usually found in the upper edge of drop-offs. They feed near the surface, away from the reef and are easily overlooked due to their size and colour.
• Clark’s anemonefish (Amphiprion clarkii) – added from our breeding stock. It took a few days for the pair to become comfortable in their anemone.

The mini-frame coral fragments have started to grow and encrust, although there are signs of bleaching due to the warmer waters (monthly average of 31°C). To reduce the tank temperature, we have started experimenting with the introduction of ice during the morning (the air conditioning cools in the evening).

The following specimens have been relocated to our large aquarium:

• Banded Coral Shrimp – where it might provide a ‘cleaning station’ to the fish inhabitants.
• Juvenile Rock Lobster – very healthy and continuing to grow at a good rate (2 moults in April).

Linckia multifora sea stars

• SS1 (large specimen) – some of the arms have decreased in length, while others have increased (the total size of all arms, however, remains the same).
• SS3 (large specimen) – average increase in arm length of 1.2mm (one arm has decreased in length). Interestingly this month, the sea star has self-amputated; autotomy is a form of asexual reproduction where the arm can grow into a new individual.
• SS4 (automised arm) – thought to be hiding somewhere in the tank.