Don't tell anyone but I haven't done a water change on a 30 gallon reef tank since May/June 2023. I don't plan on doing one as long as EVERYTHING looks healthy. I think these pics of my 7 month old corals tell the story. I got them all as frags and they have since triple and quadrupled in size and have grow to the point where I'm giving things away until my 220 gal tank is ready. This tank is NOT dosed, no water changes, has no skimmer....nothing other than a tiny 4 gallon fuge , lots of rock and live sand and a **** load of CUC. I also hardly ever clean the glass...why because my CUC takes care of that.
Raul, please stop man. Don't mean to be rude but of course we don't have the oceans amount of water. We and a tiny fraction and we base our filtration and ability to work properly for the size tank. Perfect example on 1 thing. If you have a 30 gallon tank you should have 30-50 CUC. If you have a 200 gallon tank then you should have 200-300 CUC. It's all relative to size man.