healthy corals

what is the most important to keep the corals healthy and deep colors

 

First, what type of corals you are referring to? Soft, lps, sps? I don't think there is a definitive answer here, but in my mind, the most important thing would be to provide proper light spectrum and intensity. Supplemental feeding can also benefit a coral as well as stable water parameters and good water quality.

 

There's many factors, all depends on what type of coral you're talking about: Soft coral, LPS, or SPS

- sufficient lighting
- dosing additives to keep your ALK/CA/MG levels stable
- making sure your PO4 is at or below 0
- adequate flow (different corals require different flow)
- some corals need to be target fed

 

I'm not sure there is an answer to this question. Isn't it a bit like asking what's most important to keeping a baby alive: food, water or air? ;D

Keeping a coral healthy is just about knowing it's requirements, which vary from coral to coral. Provide the requirements and you will most likely succeed, although sometimes even providing the requirements we're aware of still isn't enough, sometimes stuff happens.
The various requirements have been listed. But I think it generally boils down to providing the right water chemistry, light, water flow, temperature and food sources, all of which vary from coral to coral there's no magic global formula unfortunately.