yea, maybe 20 years ago LOL. Nothing is better for ALL living creatures than clean, pure, fresh H2O. I can do a 90% WC right now and nothing but good will come of it. All your natural bacteria lives in the filter media and in your gravel and smaller amounts on the décor. Less than 10% of your total Natural (Beneficial) Bacteria lives in the actual water column itself. Your not taking anything important out when you do a 50-90% WC
Besides, most cichlids are incredibly hardy, resilient and resistant, so while it might not be a great idea for Tetras or sensitive fish, Cichlids will love it. Just add 1TBSP of table salt per 5 gallons immediately if you are worried about them stressing over it. Salt fixes everything lol I do it as soon as I fill the tank back up w/ dechlorinated water (Stress coat is best), dry my hands and plug the filters back in