I am not sure if this is the correct forum for this question, but here goes...
I recently wen to a local restaurant (http://www.pagodahotel.com/) for a family function. The establishment is famous for its bar and restaurant that sits over a massive koi pond. Swimming amidst the koi and supersized goldfish (nice to see goldfish grow to full size!) were some large cichlids. While I am no cichlid specialist, I know that these water conditions should be acceptable. Topping it off were the "mosquito control" guys - probably guppies or "Gambusia." Here is where it gets weird...
I am a divemaster with 10+ years and hundreds of dives off O'ahu. I know my reef fishes out here cold. In this pod I saw the following (I am using "Hawai'i's Fishes," John P. Hoover, 2003 to correlate what I saw to scientific names):
- Manini / Convict Tank (Acanthurus triostegus)
Na'e'nae or palani / Orangeband surgeonfish or Eyestripe surgeonfish (Acanthurus olivaceus or A. dusummieri. It was a top view, so it was hard to tell.)
Moi / Threadfin mullet (Polydactylus sexfilis)
'O milu / Bluefin trevally (Caranx melampygus)
Ulua / Trevally (Caranx sp.; at 2-3 ft long, this bruiser was no 'o milu!)
Kaku / Barracuda (probably Sphyraena barracuda)
How is this possible?
I have been theorizing on this for a while now. At first I thought they had some hidden barriers to divide salt and fresh water fish. No; the ponds are all interconnected, with nets keeping some of the ornamental koi isolated. I know that certain big cichlids are tough-as-nails, so I thought that maybe this was a very brackish set-up. Curiosity overrode sanitation, and, yes, I dipped my finger into the pond to taste for salt. If it is brackish, it is only barely so. The reef fish show no sign of stress, so I am assuming they weren't drive-by dumpings. Only the moi are considered edible, the ulua and 'o milu being prone to ciguetterra, so I am rejecting holding tank as a theory. Most of these critters are in-shore species, subject to periodic fluctuations in salinity, so maybe they are simply tough enough to handle this. Finally, I remember a 1950-s / 1960-s vintage book in my school library 30 years ago that talked about acclimating tougher reef fish to freshwater, something that seemed dubious in the 1980-s and almost ludicrous now. Given the size of this pond, and the size of that ulua, that seems impractical in this case.
This whole thing is baffling to me, as it stretches my understanding of how fish regulate their body salts as well as my understanding of their adaptability. I would be thrilled to hear some plausible theories about this unlikely mixture.
Also, please don't bash this hotel. The ponds were clean and the fish appeared healthy. I put the hyperlink up only to help provide some evidence that what I am saying is real, not to slam them for cruelty to critters. I understand if you doubt this story. If I read this post, I'd think it was a "fishy" tale, too. That's why I am hoping someone can put science behind what I saw.