Question
I have a 500 gallon above ground koi pond.  My pond is surronded by formed cement and it has a large water fall.  During the summer it gets really hot.  My koi survived last summer but I am worried that the heat is to stressful on them.

Answer
Leslie,

You neglected to say where you are located.  Also, how hot is "really hot"?  My ponds here in northwest Louisiana regularly get over 85 degrees.  Add a large water lily or other plants to shade the surface and you should be OK.  True enough, a larger pond that might stay a little cooler would be better, but its hard to keep a small pond cool.

Good Luck,

John