Easy, peasy sunshade
Fish reared in sunny, outdoor climates can suffer from the effects of severe sunburn. And although water generally provides a good barrier against most wavelengths of ultra-violet light, middle and long U-V wavelengths can penetrate water, particularly in water of high clarity.
Water with even moderate turbidity from suspended solids, or discoloration from dissolved organic substances, usually provides an excellent barrier against all U-V wavelengths, and sunburn will not be a problem. However, if you are using a high clarity water source, like groundwater, and have an outdoor facility, your fish may susceptible to sunburn.
Fish with sunburn develop skin sores in the areas exposed most directly to the sun, the top of the head, dorsal fin and upper back, and the top of the caudal fin. The affected skin first turns a whitish color and eventually becomes patchy, thickened and creamy colored. Fins become frayed with a rough, ragged margin, and as the sores develop, the skin flakes off leaving a whitish or pink colored ulcer exposing the underlying cartilage or muscle.
An easy solution, says Adam Anton, a Fish and Wildlife Technician at Feather River Hatchery in California, is to build a simple sunshade as shown in the photo. The material list is simple, just some 1-inch PVC pipe, elbows, PVC glue, shade cloth and zip ties. The holes on top of the shade cloth are so fish won’t get trapped if they jump on top of it.