Hi bro, welcome to the forum. Adding ice cube is a very bad idea. When the ice cubes melt, it will decrease the salinity of the water. Even if you freeze salt water to match the salinity, are you going to be around every hour to maintain the temperature? I tried to work around this when I first started my nano tank by using ice packs, end up it does more harm than good, I gave up and bought a chiller.
Edit 1: I know it is bad form to complain about a downvote... but really? I get bad karma for helping a bro out when nobody else answered?
Edit 2: So Raydiative is the culprit! LOL... The price I pay for teasing him all the time, real karma lol.