Fish Lab & Marine Aquaria

Clownfish Breeding

We have established an experimental tank with a mixed breeding pair of Amphiprion clarkii and Amphiprion nigripes; they are becoming more friendly, so we are hopeful of breeding hybrids.

The Clark’s clownfish breeding pair introduced earlier this year has still not started spawning. Generally, we expect to see courting behaviour after 3-4 months, so if no eggs are laid by the end of November (9 months from capture), we will return this pair to the wild.

The Maldivian clownfish are showing cleaning practices normally associated with laying eggs, but are yet to spawn. The Oscellaris are reliably spawning, but they are consuming their eggs after several days (a common problem when breeding Clownfish).

Plankton Production

The rotifers have been going through stages of high and low numbers, mostly attributed to sulphur bacteria and ciliate contamination during the previous months. Despite the continued presence of ciliates in our samples, the rotifer count has steadily risen from mid-October, and while there have been some dips, we are still working at over double the concentration from when ciliates were observed in large numbers.

We have been using UV-sterilised salt water and filtered freshwater to provide the best quality water for the rotifers, and committed to preparing yeast solutions in glass beakers instead of plastic bottles; both methods seem to have eliminated the presence of bacteria, and greatly reduced the levels of ciliates. We have kept the food ratio at 1g/200ml, to reduce the food available to the smaller ciliates, therefore limiting their growth and reducing the risk of competition. This method has shown daily increases of rotifers, with minimal increase of ciliate numbers. We are hopeful this method will eliminate any ciliates left in the tank, once the higher volume of rotifers out-competes the ciliates.

Little has changed in the artemia production. We are continuing to have greater hatching success by removing bleach from the process, and hydrating with saltwater only. We have also taken to keeping them outside, to allow maximum sunlight and a more natural temperature.

Algae production continues at half-capacity (since Apr 2020), as we do not have any hungry Clownfish larvae to feed.

Linckia multifora sea stars

• SS1 (large specimen) – started to look unhealthy, so we relocated it to our coral pool (larger, with better water circulation).
• SS3 (large specimen) – short arm has grown significantly this month (see image, depicting sizes from May to October).

Large Aquarium

We have been performing maintenance tasks on our large marine aquarium, and the temperature has stabilised at 28.9°C (a little too high). One of the UV lights failed, so we are borrowing 2 lights from the coral project. This has dramatically improved the lighting quality, so we have added some new soft coral specimens. We have also observed some of the Sclectarian corals start to encrust onto the substrate (a good sign).
The aquarium’s inhabitants are all actively feeding and are largely healthy, with natural movement around the tank, but we have decided not to add any new fish until we can capture the overly-aggressive crabs!

Small Aquarium One

• Mini coral frame – 7 fragments are growing and remain healthy, and the hermit crabs are grazing on the excess algae.
• We also introduced a Galaxea fascicularis to the aquarium (a different colour morph to our existing specimens).

Small Aquarium Two

• Mini coral frame – tissue loss and some mortality of the Acropora digitifera.
• Clark’s anemonefish (Amphiprion clarkia) laid eggs three times this month.
• Blue damselfish laid 2 batches of eggs (under a mushroom coral, so difficult to study).
• Galaxea fascicularis specimen in aquarium 2 (pictured).

Jellyfish – Aurelia aurita

We now have 5 tanks of growing jellyfish:
(1) polyp tank #20, (2) small-jelly Kreisel, (3) a medium-jelly Kreisel, (4) a large-jelly Kreisel, (5) main display.

All the water is now being UV-sterilised and changed every three days, resulting in much reduced growth of algae (especially noticeable in the main display tank).

By the end of October, we totalled 1360 jellyfish, with tens of thousands of polyps ready for strobilation [*]. We are currently investigating tank designs, and might start to sell our Aurelia to hobby aquarists in the Maldives (international prices are $20- $70/jellyfish, dependent on size).
[*] Strobilation is defined as asexual reproduction by transverse division of the body segments which develop into separate individuals.

from: Jellyfishes – Diversity, Biology