Top 5..or 10... MUST haves for a reef tank

[super7]

good lighting, cycled tank, flow.
Skimmers are not needed for small tanks,
what size are you planning?
super7

[kam]

I have a 125gal... 6 ft

[super7]

probs need skimmer, unless you plan on 25% plus waterchanges weekly lol
super7

[lastlight]

unless you're away from town for days your lighting timer failing on or off won't be a deal breaker... you'll notice. But temperature control is a must. If you don't want to rely on a fancy controller buy a ranco etc. $100 and you have bullet-proof temp control. other than that a tunze osmolator ATO like others have said.