Be careful. I lost a gold flake, blue face and MI to this, presumably

Depending on how large the tank is, it could take a few hours. Lights off will increase the o2 consumption by the tank (algae, bacteria, etc).

20 minutes in and no noticeable difference in fish health.
-emperor is hanging below the feeder ring
-golden comes and goes through the rocks feeding on whatever it is as usual
-moorish is hanging out in th surf picking on anthias as usual.
I'll turn down the vortechs to 70%

Good idea...
Not really a control, but at least gives this topic a better sample size to draw a conclusion...

The funny thing is that if somebody with 10 posts, regardless of their actual experience, tried to say that a certain genus of fish was dying in their tank and the ONLY reason could be low oxygen, this board would be all over them telling them to test this, test that and double check everything...

That or condescend for buying a fish that is considered high risk and unlikely to survive in the first place.

If the MI isn't eating yet you need to bring out the fish crack... Pacifica Plankton. I kept a MI alive with it for 3.5yrs. Big, fat and healthy.

Speaking of oxygen demand I just got back from Hanauma Bay where I observed lots of MI pairs and Achilles pairs all in 4 to 8 feet of water and not a lot of current. Even got side swiped by about 300+ convict tangs as they raided the reef where an Achilles pair were living. Their territory was only about 4' by 6' and they were about 7" long. Think I need an Achilles in my 4' by 8' coral tanks. :-)

Tim, sorry, mine is eating well on a competitor's shrimps :) I may have some plankton in the freezer though, I'll try that tonight.

An hour in and I see no noticeable change in fish energy.
Threw some nori in for fun and it was the usual frenzy.
Total volume is over 500 gallons so I'll give it another couple hours. My sump turnover is around 8x per hour which could be a significant source of oxygenation but I would assume that with the skimmer off the DO would drop some...

One of the most frustrating things about this hobby is the number of variables from tank to tank.

I would imagine that your salt would also play a role in your tanks ability to store oxygen as would it's proximity to outside air...

This could be a pretty neat discovery if it turns out to have some merit.

Are lights off? if you have your lights on and have algae, you would be getting O2 from photosynthethis from the algaes in your tank.

Regardless of post count, I'm as experienced as the guy with 10 posts in this topic. I do have dead fish with no other explanation, but that's all I've got. I'm not will to try and replicate it to test :)

As for the morality of buying these fish, it's a topic for another thread, which I will bring up when I have more time to type.