This post won't offer anything for an experienced aquarist, but if you're relatively new to the hobby, keep reading. Because cichlids are tropical fish and are endemic from mainly warm climates, their watery home is usually pretty warm. Sure, deeper water cichlids like from the Rift Lakes in Africa can experience mild fluctuations, but for the most part, cichlids live in water that is in the 70s and 80s Fahrenheit.
If you're new to freshwater fishkeeping, most fish in the hobby require water that's in the same temperature range. One key to good fishkeeping is to mitigate stress in your fish, and one way to accomplish this is to maintain a steady water temperature. Most captive fish have been conditioned for living in a reasonably steady state with respect to water.
The point is, whatever cichlids you keep, make sure you try to maintain that safe range, which most experts will say is between 76-80 degrees Fahrenheit. So how do you change the tank water and ensure the temperature doesn't fluctuate wildly each time? The obvious answer is to use a thermometer to gauge the temperature of your source water. You can buy aquarium thermometers at your LFS for a couple of dollars and just run them under your source water until you have the right temperature.
The good news is you won't need to do this forever. Eventually, you'll be able to feel the right temperature with your fingers and will no longer need to depend on a thermometer. I haven't used a thermometer to measure my source temperature in years.
In fact, I keep my 75g Tanganyikan cichlid tank at 77.2. I did a 40% water change this morning and the temperature after the change was.....77.2. Not bad to get it to the exact tenth just by feel.
The Cichlid Room Companion
Tropical Fish Hobbyist
American Cichlid Assoc.
African Cichlid Hub