When he get's accustomed to your tank, he will not retract as fast as he does, he will simply react and re-open. Mine use to do that, now he just twitches when he see's a shadow because he's grown accustomed to my fish stock. I occasionally pass my hand below the halide to simulate a large fish or sting ray passing by, looks pretty cool.
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30g reef tank, CPR CY192 filter w/ DIY plumb running Rio 17HF return, Coralife 3x 9w UV Sterilizer, 3 24W T5-Helios 10K Daylights/3 24W T5-Helios Blue lights, 2 Logysis blue meteor light strobes (moonlights/24 Blue LEDs).
Tiger tail cuke, asst. snails/hermits, asst. feathers, rainbow acan,zoos,shrooms,bubble,galaxea, asst. shrimp, 2 ocellaris,mandarin,zebrasoma xanthurum,pink-spot watchman,red-striped pistol. | 
dang lazy cleaner shrimp! 
