question about water changes and those guys that hang out at the top of the tank!

[sh8wn9]

My urchin has decided to take up residence at a different section of the tank. Now it likes to hang out at the very top of the tank corner between a powerhead during the days. That got me wondering about water change because I need to do one this week. I never really worried about the occasional snails being out of the water for a bit, but is the urchin gonna be ok.
Im afraid that when I change the water, its gonna be out of the water for too long? Does that affect creatures like snails or hermit crabs, or do they have enought sense to just let go and fall back into the water???

 

[BigAl07]

Keep in mind that many creatures in the ocean up next to the shoreline can be "air exposed" for a few hours at a time. The only time I worry about something being exposed to air is if my lights are gonna "FRY" it out of the water.

 

[sh8wn9]

OK thanks for the info. Its kinda like a low tide I guess.