I need to lower my tank temperature to 74 degrees. It has been always been at 78 degrees, but I recently learned my Gourami's labyrinth organ is susceptible to damage if the water temp and ambient room temp is too different. Apparently the Dwarf Gourami is best kept at a temperature range of between 72 and 82, and the room temp is about 73 to 74, so 74 sounds like a good number. My other fish fall within this range as well, so everything should be fine. Question is, how gradual do I need to decrease the temperature? Can I simply set it to 74 and let it be? It's a 20 gallon long, so it will take a few hours to drop anyway.