I ran reef tanks for 10 years before I ever started Zeovit, and there were times those tanks didn't look too bad.
I'm still only about a half believer in the zeo.
I'm really not a fan of daily manual dosings. It's not a big deal for me but I hate asking people to do it when I have to go away for whatever - if it's too complicated a process, they'll never tanksit again. And never mind the "oh and pump this handle 15 times in the morning, and again 15 times in the evening, if you would, please and thank you."
I had the cyano thing too. I did get a marginal improvement after I dosed red slime remover. No more cyano and no signs of it reappearing. However, the film algae on the glass is out of control. Although it's weird, it must be the sand because the 40g carpet tank (same sump == same water) does not have a film buildup on it at all - I clean it about once every 6 weeks or so. But the 75g main display - needs the glass cleaned on a daily basis. If I let it go beyond 2 days, the magfloat doesn't clean it anymore - I have to use a razor blade at that point.
I think the difference though is that the 40g has a large stomatella population but the 75g has a small population. I'm not sure who's picking them off but I suspect someone probably has a taste for them. At any rate, point being, I'm not so sure my 40g clean glass is really attributable to the zeo.
So basically I just use zeo for the water clarity and as a substitute for GFO. ... Can't really say I ever saw the crayon-box colours come out of my corals that you see on all the zeovit pictures.