I built my first pond about 3 weeks ago. it is a liner kit with skimmer and waterfall, rocked in. Picture in my profile. We put in 2 goldfish from neighboors pond, 3 years old. # days later we added 3 small feeder goldfish from petstore and 2 pet store shubunkin. We had a total of 7 fish between 1.5 - 3 inches. On August 2nd we lost a feeder. On August 5 we lost a Shubunkin . We added a new older Shunbunkin on August 4th. On August 10 we lost another feeder. In most cases we watched them one by one detach from the group and become more secluded and stop coming up to feed and then die. Now we have one of the three year old goldfish behaving oddly. At first she was being chased by two of the other fish and we thought she might be a female and they were trying to get her to release eggs. Yesterday she was hanging out, not swimming near top of the pond on the skimmer side. This morning I could not find her when I fed them. It has been very hot and humid the last few weeks. The water tests come out fine. Water temperature is about 80. I had some water lettuce and hyachinth plants and recently added a reed and arrowhead. Yesterday I added more water lettuce to further shade the water. I can provide more information if needed, but someone please help with some ideas. My daughters are sad that they are losing their named fish. Maybe I need to change water...but so soon? Maybe the waterfall is not providing enough aeration? it is odd that they are dying one by one. Please help with any suggestions.