Cindy’s 20-year-old Opaeula

These are two of Cindy’s small opaeula tanks. These semi-sealed bottles are approximately 7.25″x4.25″x4.25″. She bought them from a coworker in April 2002, so some of the opae are at least 20 years old. Photo by Cindy Hirai.

Cindy Hirai bought two of her semi-sealed bottled opaeula colonies (see photo above) from a coworker in April 2002, so some of the opae are at least 20 years old. Her other bottled opae, elsewhere in the apartment, were obtained later. She’s opened these two small tanks around three times in all these years to top off for evaporation and to clean the inside of the front-facing glass. She’s never fed them or used any sort of mechanical filtration. The tanks are as she got them, with algae growth over the years.

Cindy Hirai.

In the beginning, there were ten opae in each tank. The ones in the tank on the left haven’t reproduced, but the ones in the other tank have been prolific. She believes the colony has grown to at least a hundred.

The opae are kept in a bedroom, which has a large north-facing glass sliding door. No direct sunlight enters the room, and the tanks are on a shelf against a wall in the middle of the room, so exposure to sunlight has been limited. She doesn’t use any artificial lighting, except for the room’s ceiling light that’s on from time to time.

Cindy’s ancient opae goes against the grain of popular belief that opaeula in small sealed bottles don’t reproduce. In fact, she has not only replicated Dr. Wayne Nishijima’s findings that opaeula, with a minimum of maintenance, are long-lived, but she has also proven that they can and will reproduce.

Her experience also proves that opaeula in small sealed bottles can reproduce with minimal maintenance. This is an amazing revelation. However, the fact that most opae in small containers don’t reproduce may be a sign that Cindy’s opae are an exception.

What makes them an exception? I’m guessing that the tank on the right (see photo above) replicates, to some extent, the anchialine conditions in their natural habitat. The decorative shell that dominates the tank floor has holes leading to the dark interior chambers of the seashell, much like the spaces between the mounds of coral rocks that Dennis Nakashima has pioneered and referred to as “condominiums.” The assumption is that these dark tunnel-like spaces are essential for breeding. The tank on the left also has a decorative seashell, but it doesn’t seem to be as extensive.

Cindy also observed that opaeula do eat their dead, contrary to the opinion that they don’t. In this way, the ecosystem is self-sufficient.

18-gallon Opaeula Tank – Video 8 April 2019

Moved 10-gallon Opaeula Colony into the 18-Gallon

The 18-gallon close to the south-facing lanai windows.

Downsizing my opaeula hobby to 2 tanks: 18-gallon & 1.5-gallon. Keeping the 2 that require the least amount of maintenance. The 18 seems crowded, but the opae seem to be fine. I’ve seen a couple of berried females, although they don’t show up in the short video below.

For more on the 1.5-gallon, see “Experimental Oblong 1.5-gal Tank” and “Aqualifter Pump+Filter Change for Small Tanks.” The opae in the 1-gallon tank were also moved into the 18-gallon.

These remaining two tanks are healthy and require very little maintenance. I haven’t done water changes in years. I seldom need to top-off (both are hooded) and salt creep is not a problem. I’ve never had to clean the glass for the 1.5. I haven’t cleaned the 18 glass in over a year. This tank gets a lot of sun, so I may need to do a cleaning of the front panel glass when it gets too overgrown.

I’ve never fed the 1.5. Since combining the 10 and 18 colonies, I’ve been dropping tiny pieces cut from a dime-sized algae chip into the 18 once a week. I don’t think this is necessary since the algae growth in the tank is robust, but they seem to like it.

The 18 is filled to the 10-gallon level to prevent salt creep, and this arrangement seems to be working fine. For the 18, I run the UGF pump for a few hours each day. The 1.5 is still using the Aqualifter system, which runs 24/7 with a very light flow. I may need to clean the tubes when they become clogged, but they’ve been fine so far.

DIY UGF for 1-Gallon Tank

This DIY UGF is slightly different from the one I posted in February 2016.

Click image to enlarge.

Opae’ula Breeding at Record Pace in the 10-Gallon

Opae’ula Post-Larval Stage

The opae’ula pre-adult development cycle lasts approximately 11.5 weeks. The brooding period is 38 days. The larval stage involves two substages: zoea (17 days) and megalopa (11 days). The final stage before adulthood is juvenile (14 days). Adults are theoretically able to live more than 20 years.

In the larval stage, the opae are limited to moving vertically only or hanging suspended in the water. They remain upside down, with their head pointed down and tail pointed up. In the post-larval juvenile stage, they begin to move horizontally and diagonally. In this video, we see them (tiny dots) just beginning to swim sideways on their own.

Keep an eye out for a berried female. There are three or more in this tank. Females can produce more than once per year.

Acknowledgment: Soundtrack “Alta Loma Terrace” by Wes Hutchinson.

Opae’ula Juveniles – Growing Population

Third Batch of Zoeae – Baby Opae’ula

Last updated 2/19/18

Update 2/19/18: Correction: The zoeae are probably from the same batch reported on Jan. 29.

Opae’ula Zoeae – Another Batch 3 Feb 2018

Last updated 2/19/18

Update 2/19/18: Correction: The zoeae are probably from the same batch reported on Jan. 29.

A Dozen Opae’ula Zoeae in 10-Gallon (West)

Last updated 2/19/18

A dozen opae’ula zoeae in 10-gallon west-facing tank. A few berried females, too.