my boyfriend has had an outdoor Koi pond for 4 years. I moved in last year. I am new to all this. He had 4 and 1 died last week. Well, this morning I saw that another had died. I have one water lilt plant in the pond, but I also had a couple of potted plants on the rock around the pond. My question is: could me watering the potted plants and the water running into pond been the reason they both died? I feel so horrible! I should also include that he had 4 koi in a 100 gallon pond. I have done some research and read that koi need bigger living spaces. Help!