So many great comments so far, little to add, maybe just +1 on some....
The best warm water stuff at night can easily be found
in the shallows. You will see more Octopuppies and Squidlets in <25fsw than any deeper.
My wife has mastered certain techniques so that she can entice either to make contact with her hand or mask faceplate. They are cautious but curious.
The critters
seem to be out more at night, indeed they are more adventurous (out of their hidey holes),
but many hide in plain sight all day long. Octos could pass for the critter Predator from the Arnold movies. Amazing how blind we are.
A
back-up light is a minimum requirement. (Two is one, one is none)
Get very
familiar with the dive site during daylight hours. I did three day time dives on the Thistlegorm in the Red Sea pushing my nitrogen load pretty high- it was worth it for the night dive. I have done the "Front Yard/Prince Albert Wreck" at Cocoview several hundred times- I have never been lost at night~ but I can teach the willing and competent the landmarks in 30 minutes time. Familiarity of the terrain makes for a longer and more comfortable dive.
Skip the camera for the first few- until you sort it all out. If you find a good local DM, hire him to show you the critters.
Glow Sticks are fairly useless, you can only use them to find your buddy among the masses, but only if he's the only one wearing one. It's better to tie a colored flagging tape to your ankles or tank nipple. For illuminating a SMB, nothing beats
putting your flashlight up to it- a glo stick might be seen by a helicopter with FLIR, but useless for a boatsman.
Never turn off your primary light. Instead,
cover it with the palm of your hand or stuff it in the armpit. It is, of course, secured to you with a lanyard. If you croak out, at least they'll have a chance to find you. If your light was off while you were gawking, well....
My best such experience: In a screaming current of about 3mph, zooming along a shallow depth of a sloping Philippine wall in Puerto Galera. Lights covered. The Plankton in the current looked like thousands of popping flash bulbs against hillsides of Christmas Trees- they were Chrinoid Stars extending their tentacles for the night's meal. A light show that was amazing. Drifted along for 20 minutes in the Moonlight.
Feed the fish with your light. Learn how the critters will use your illumination. Yes, some apex predators will hunt with your light. Large Jacks and Rays are very interested in what you are looking at or attracting in the water column.
When people ask me about
Night Life at a dive destination, night diving is all I can reference