Many reptiles use UVB to produce vitamin D3 and absorb calcium. Inadequate exposure can contribute to metabolic bone disease, but visible brightness does not show how much UVB reaches the animal.
Design for the species
Choose output, distance and exposure for the species rather than from wattage alone. Glass blocks most UVB, mesh reduces it and intensity falls with distance. Align useful UVB with the basking heat zone while retaining shade and cooler hiding places.
Maintain the system
UVB output can decline before a lamp fails visibly. Record installation and replace according to reliable specifications. Diet, calcium-to-phosphorus balance and temperature also matter. Weakness, tremors, deformity or a soft jaw needs prompt reptile-vet assessment.
