Fish Lab & Marine Aquaria

Clownfish Breeding

We have installed new dimmer-controlled lighting above our larvae rearing tanks, which means we can now adjust the light levels to promote more active feeding and growth amongst the larvae. We have also installed lids on the breeding tanks, which we hope will reduce stress among the fish.

We are currently satisfied that the diet is nutritious enough to produce high quality eggs, and will continue following the same feeding protocols for the foreseeable future.

• Clark’s Clownfish (Amphiprion clarkii) – mixed success, prompting a reshuffle of the breeding pairs. We have released one pair into the main aquarium, and introduced a new large breeding pair caught from the reef. We are hopeful that this breeding pair will start producing eggs in the coming months. Breeding pair #2 is regularly producing eggs, with three spawning events in March producing healthy juveniles.
• Maldivian Clownfish (Amphiprion nigripes) – one breeding pair laid 2 egg batches during March, however, they eat the eggs prior to hatching, so we moved the pair (with an anemone) into the main display tank to provide a more natural environment, to see if the behaviour continues.
• Common Clownfish (Aphiprion ocellaris) – we have successfully reared three individuals to juvenile stage, which we hope to increase if production continues.

March has again seen an increase in the Fish Lab population, with tank occupancy increasing by 10%, and the number of individuals rising by 50. New inhabitants include a breeding pair of Banded coral shrimp (Stenopus hispidus), and we are monitoring the growth of a juvenile lobster specimen.

Small Aquarium One

The juvenile Maldivian anemonefish (Amphiprion nigripes) has grown in size and is better acclimatised to the aquarium, spending more time near the corals. The new zoanthid colony (Zoanthus mantoni) has been predated (by crabs or the seastar) resulting in a loss of polyps.

A new G. fasicularis coral mini-frame has been added, and we are experimenting with various transplantation methods (proximity, contact point, fragment size & orientation). Our Acropora coral mini-frame was showing some bleaching and tissue loss, so we removed the diseased fragments and relocated the frame to our coral holding tank for observation. 17 out of the remaining 21 fragments are now encrusting,  and interestingly they show some interspecific growth variation (A. latistella is encrusting to the bar not the zip tie, whereas A. hyacinthus has grown over the zip tie but is not yet encrusted to the bar).

Small Aquarium Two

We have seen an increase in algal build up, particularly on the coral plates and rocks. This has also affected the mini coral frame, which was cleaned of algae (greater on the shaded side of the frame). Any paling corals were removed, and this frame was also relocated to our coral holding tank. 11 of the remaining 16 fragments are healthy. The Clark’s anemonefish laid 3 clutches of eggs this month, and we observed that (photo):

• Day 2-3: the eggs undertake significant organ development from the yolk sack.
• Day 7: on all 3 occasions, the eggs hatched overnight (with a few individual eggs hatching on Day 8).

Moon Jellyfish (Aurelia aurita)

With the loss of our UV-sterilising light, the water quality inside the Kreisel tank has reduced, resulting in some fatalities amongst the jellyfish. A new light has been ordered, but until it arrives, we have transferred the jellyfish into a tank inside the Fish Lab. This will provide cooler water temperatures, increased water turnover and greater amounts of food.

Large Aquarium

We have increased the monitoring of our large marine aquarium, to more carefully control the environmental parameters during this season of increased ocean temperatures. The overall temperature of the tank has risen from an average of 28.8°C during February, to over 29°C consistently during the last 2 weeks of March. As a precaution, we have reduced the water flow during the day so that the cooler air temperature may stabilise the water temperature. The pH levels spiked during week three, but is now comfortably within the recommended range (as are the ammonia and nitrate levels).

Our main aquarium has had some new additions during March, including:

• Harlequin shrimp (Hymenocera picta) – feed exclusively on sea stars of all sizes, even crown of thorns. Live in pairs in the wild. Our specimen arrived as a larva on a rock.
• Bicolour blenny (Ecsenius bicolour) – popular aquaria species that are great at cleaning the microalgae from rock. They are shy, often sheltering before appearing to feed.
• White belly Toby (Canthigaster bennetti) – small species of puffer fish that feed on benthic algae and small crustaceans. Our pair can often be seen grazing around the tank.

Linckia multifora sea stars

SS1 (large specimen) – average decrease in arm length (for the second month in a row) of 0.2mm, either due to small variations in the accuracy of our measurements (especially with curved arms) or perhaps the seastar does not have sufficient nutrition.

SS3 (large specimen) – average increase in arm length of 1.8mm (continuing the increased growth rate).

SS4 (autotomised arm) – this month, hiding amongst the rocks!