it works well but the setting was done by successive attempts. Indeed, the water of the aquarium (15 liters) was initially at 19 ° C. After instalation of "heating" set at about half power, the temperature rose to 26 ° C. I quickly set to minium and now the water is between 21 ° C and 22.5 ° C (depending on the outside temperature). So I was a bit scared for my fish because the temperature difference 2/3 hours was more than 6 ° C ... but good, no breaks, all fish survived and are doing well (see better than before).