Depth required depends on species, shade, water movement, and latitude. Also fish density.
Fish : gambusia/minnows can survive in 2" water in shade. Green sunfish - 4-6" in shade. Mudcats - 4-6". Largemouth bass 18" in shade.
My pond (no shade)went dry in late July w/100 F days. At about 30" massive fish kill
occured. Channel cat, bluegill, and green sunfish died. Gambusia and some under 2" green sunfish survived. At about 6-8" all sunfish were gone. The last Gambusia died in the cattle hoofprints as it dried up . The recommendation for 3' minimum depth makes sense. Allows for some level fluctuations and aids in freezing protection in winter. Shade is good thing as is water movement. Gambusia and green sunfish are excellent at mosquito control. Black bass will aid in cotton mouth snake control
as they will eat baby snakes that enter the water.
