Loop Diuretics
These are diuretics that exerts effect on the loop of Henle. They are primarily used in heart failure, hypertension and edema. In contrast with Thiazides, loop diuretics are more effective in patients with abnormal kidney function. Loop diuretics inhibit the magnesium and calcium reabsorption in the thick ascending limb of Henle. Loop diuretics is highly protein bound. It has volume of distribution that is limited. This causes the diuretics to be secreted in the convuluted tubules to exert its function.
Hardness is the answer I believe
Why temperature affects heart rate in ectothermic organisms? If the temperature is within the optimal range for enzyme activity more ATP will be produced and the heart will beat faster due to increased metabolic activity and energy availability.