Dennis Nakashima: Opae’ula Guru and Good Guy

Last updated 11/1/14

“500 opae’ula or more!!!” Uploaded to YouTube on 6 Feb. 2012 by Dennis Nakashima.

Dennis Nakashima

Dennis Nakashima

Nakashima bought 28 opae’ula from Fuku-bonsai, and in seven years the population had grown to approximately 500 or more. He says that, for the first 15 months, they didn’t breed. “Be patient,” he advises, “it’s going to happen.”

From the discussion appended to the video above and, to a lesser extent, from his other videos below, I gathered the following information about Nakashima’s method:

1. He doesn’t feed them. Instead, he places them in indirect sunlight where algae can grow naturally in the tank. The opae’ula feed on algae. The result is a self-sustaining regenerative ecosystem.

2. He uses tap water in his brackish mixture, which he describes as “1 part sea water, to 7 parts fresh water.” He gets the salt water straight from the ocean. He says, “I only refill fresh water from the garden hose when needed.”

3. He found that opae’ula can survive in sea water. (See his June 2013 video below.) He says, “They can handle a wide range of salinity…. Right now I have about 200 opae’ula in a marine tank. The salinity is the same as the ocean! It’s a 20 gallon aquarium that is outside the house with a powerhead to keep the water clean. It’s in direct sunlight.”

4. He doesn’t do any water changes.

5. He doesn’t use a mechanical filter of any kind. He says, “No filter. Just leave the tank alone and refill fresh water when needed.” (See his June 2013 video below re an undergravel powerhead filter in his experimental opae’ula tank.)

6. He keeps a two-gallon tank in the bathroom, on the northeast window ledge. (See the April 2008 video below.) He says, “The population grew to around 80 shrimps. That’s without feeding them.” However, in the June 2013 video discussion (see below), he says, “I had my entire colony wiped out, because of an insecticide bomb that was used in an adjoining bedroom. All 80 or so opae’ula died.”

7. He uses only fresh tap water to clean tank items. Opae ‘ula “are very sensitive to chemicals,” he warns. Thus, clean “only with fresh water, no soap or any kind of detergent. Just rinse it out with fresh water. Any kind of chemical may result in death with your opae’ula” (from the June 2013 video discussion).

8. He suggests “lots of indirect sunlight.” He says, “The more indirect sunlight, the better and healthier your opae’ula.” For indirect sunlight, he says, “I try to place my tank on the north facing side of the house.” However, see 3 above, where he found that they can also thrive in direct sunlight.

9. This is how he describes the baby shrimps: “Once they hatch, the babies will float around for about two weeks, if I remember correctly, with their heads down, tails up. You will see them moving about seemingly floating up and down the water column. Later as they mature, you will see them crawling like the adults.” See Hmoob Thor’s “Opae Ula: 2nd Batch of Larvae” (24 Aug. 2014) on YouTube for a beautiful video of the larvae.

Interestingly, except for the last three items, the first six are in stark contrast to what other experts suggest.

In his June 2013 video below, Nakashima describes his experiment with an opae’ula tank that’s all sea water (not brackish), outdoors in direct sunlight, and equipped with an undergravel powerhead filter. It seems to be successful.

His bathroom tank also contradicts many experts who warn against placing tanks in bathrooms and kitchens where temperature fluctuations may be too great. His “colony” died, but not because of its location.

“Opae Ula Outdoors.” Uploaded to YouTube on 5 June 2013 by Dennis Nakashima.

Nakashima raises some very interesting issues. I’ve just begun keeping opae’ula, and I’ve been religiously following conventional wisdom. In time, I plan to explore some of Nakashima’s practices, and I hope others will, too. The tiny Hawaiian shrimps have become very popular pets, but we apparently don’t know very much about them. Pioneers like Nakashima are forcing us to re-examine what we think we know.

“Opae’ula…no biosphere.” Uploaded to YouTube by Dennis Nakashima on 21 April 2008.

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