I've had my goldfish in a 200 gal. garden pond for about 10 years with no problems but suddenly they became listless and settle on the bottom of the pond all day. My water tests show no problem so I decided the water was too warm although it is always hot in the summer in South Texas. The temp ranges about 85. I've put frozen water in ziplocks in to cool it a little but doubt that does much good at this point. Today I noticed their eyes have started bulging. Any suggestions?