To get it out use an airline tube instead of a big vacuum. U just skim the surface and u don't lose a lot of sand. Even if u do its like a handful. I used a 1/4 or a 3/16 innch I think because all the little stones and shells clog up the smaller ones. Leave ur lights out for a couple days and ur coral will be alright.
Instead of actually changing the water if the cyano
gets really bad siphon out the cyano
and filter the water u sucked out. Then return the filtered water to the tank because u know that it is nutrient free water (it had cyano
in it so ur good). Do that every day or two till ur problem is gone along with the usual preventative measures. I have fixed numerous tanks with that method.
I know ur going to say I use ro
do water. Doesn't matter this is the best method everyone I know has used used to fix the problem. Plus u don't have to waste salt