I agree with Tony as well.
I have seen nice looking sps tanks that use zeo and plenty that don't. IMO colourful sps has several variables, one many people don't discuss is genetics. Not all corals of the same species will look exactly the same so don't expect it. Although you can often get lucky with unknowns I generally prefer to get pieces that are from known good parent colonies because over the years I have bought my fair share of duds that I thought might have potential but never lived up to my expectations. That said, low nitrates, minimal alk & ph spikes are key. Proper flow, lighting and skimming are also major parts of the equation. I personally don't use zeo and for the most part have managed to achieve pretty reasonable colour. Using zeo or not is a personal preference and good results are not guaranteed with any husbandry method unless proper care is provided.
Because I tend to over stock my tank with both fish & corals I use an oversized skimmer and dose with AA's to help lower my nitrates. Some may call it a lack of skill or cheating on my part which is fine but I only do a 10% water change every 5-8 weeks so for me it's worth it.
For the
"that's a fact" comment here is an example from my tank that I think has colour due to genetics and a healthy environment, not zeo or even AA's. Who knows, with zeo it may get better colour? I don't know but in reality this picture although bright doesn't really do it justice.
(I disturbed it before the picture so the polyps would retract to better show the coralites)
