ive had a koi pond built in my yard for nearly 2 years now. typically during the summer months when the weather is hotter my pond does loose some water due to the heat. i typically have to fill it up maybe a few times in the summer and i have done this in the past with all my fish in it using an chemical from a pet store to remove the harmful chlorine from tap water. well last nite i did this again and didnt have to fill it any more than normal and i go to feed my fish today for find i have 25 dead koi's. i definitely want to avoid this from occuring again. is there anything you can suggest to combat this or does anyone have a better idea of what they do to add water to their pond. my pond is above ground so water will evaporate quicker than that of a in ground pond. if more info is needed lmk. thanks in advance.