How often should you replace a terrarium's UVB bulb?
A UVB bulb often keeps lighting normally well after its useful UVB output has dropped sharply, which catches out many keepers who judge it purely by how it looks. Replacing the bulb on a fixed schedule remains the only reliable way to avoid a gradual deficiency.
Why does visible light give a false impression of UVB output?
The UVB spectrum, invisible to the human eye, degrades much faster than the visible light emitted by the same tube or bulb. A reptile can end up without effective UVB for weeks while the lighting still looks perfectly normal day to day.
What replacement schedule should you follow?
- T5 HO tubes: around 10 to 12 months of continuous use, even if the bulb still lights up fine;
- T8 tubes: 6 months, since their UVB output degrades faster than T5s;
- Compact UVB bulbs: also 6 months, with the drop in effectiveness sometimes even sharper;
- Mark the install date directly on the base or in a logbook rather than relying on memory.
These pointers complement our reptile accessories section for keeping the terrarium properly equipped over time.
Is a dedicated UVB meter worth buying?
A dedicated UVB solarmeter is the only way to objectively check real output rather than relying on a generic schedule. For keepers with several terrariums, the investment pays for itself quickly by avoiding both unnecessary and, conversely, overdue replacements.
What happens to a reptile deprived of effective UVB?
A UVB deficiency limits vitamin D3 synthesis, which disrupts calcium uptake and can lead to bone problems over the long term, especially in diurnal species that rely heavily on this input. Signs often stay subtle at first, which makes prevention through regular replacement all the more important.
Frequently asked questions
Do all species need UVB?
Most diurnal lizards and tortoises have a strong need for it, while some nocturnal species can do without, depending on recommendations specific to each animal.
Should replacement follow a fixed date even with light daily use?
Yes, UVB degradation mainly depends on time elapsed since first switch-on, regardless of how many hours it runs each day.
Is a broken UVB bulb dangerous?
Replace it immediately and avoid any contact with glass fragments, which can injure both the animal and the keeper.
This guide is part of Planète Pets’s Reptiles universe. Our advice is general in nature: for any health concern, your veterinarian remains the only reference.