All about Indian & Burmese Star tortoises, Angulates, and Golden Greeks...

Indoor UVB Lighting for Tortoises

- stars & other small, dryish area species -

long T-5 HO fluorescent UVB tubes

T-5 HO fluorescent UVB lamps for reptiles by Zoo Med and Arcadia (2012).

Best UV for tortoises

The best UVB source is the sun! An outside enclosure is a must for tortoises, even if they can only use it part time. In addition to the necessary UVB exposure, outdoor exercise, like walking and climbing, is immensely important to tortoises' well being. Weather permitting, let your adult tortoises roam outdoors as much as possible and take young ones for shorter outings.

If you live in a warm climate and your tortoise spends most of his days outside with free access to the sun, you won't need to use UVB bulbs. Cost of UVB = $0.

On the other hand, if you live in a cooler climate with a very short outdoor season, it's important to use reptile UVB lights indoors in addition to non-UVB basking bulbs and heaters.


a.) Quality

When purchasing UVB lights, always buy good quality reptile specific bulbs from trusted manufacturers like Zoo Med and Arcadia.

Cheap, copycat bulbs of unknown brands can emit dangerous UV radiation, for example, a too high level, the wrong wave length, or the wrong type. Tortoises need UVA and UVB, but not UVC which is harmful to them.

It's best to buy UL listed and prewired reptile lighting and heating products. Any DIY electrical wiring can be a fire hazard. Unless, you are an electrician and know what you are doing. :O)

b.) Follow manufacturer's instructions

Always attach lighting and heating devices securely and according to the manufacturer's directions. Improperly installed tortoise enclosure fixtures that have become loose and fallen off have caused many house fires.

Also, do check the minimum installation height for your specific UVB lamp and the recommended Ferguson UVB zone (see UV readings page) for your species.

c.) Lamp stands

Zoo Med reptile lamp stands work well with most dome type light fixtures. They are adjustable in height and depth and allow you to position lights exactly where you want them. They come in two sizes. I like the bigger stand, model LF-20, better because it has a larger foot that makes it more stable.welding ground clamp

d.) Caution with clamps

Avoid attaching light fixtures by their clamps. Clamp fixtures can slide down to one side, or even fall off, and start a fire. Using a reptile lamp stand and a bulb fixture that has a metal hanging loop is a safer way to install lights. If you have to use clamps, try double securing them with welding ground clamps (pic). Welding clamps have a very strong grip, but other heavy duty steel spring clamps work as well.

e.) Hooks & brackets

UVB and heat lamps can also be installed securely by suspending them from sturdy ceiling hooks or wall brackets. Light fixtures that have built-in hangers, for example, domes with metal loops on the top, are easiest to use. Lamps should not be hung by their cords.

f.) Smoke alarms

Keep hot bulbs away from any flammable materials like enclosure covers or nearby curtains. Do install smoke alarms in your tortoise room, garage, basement, or where ever you keep your heated indoor enclosures.

UVB & basking

Tortoises need access to UVB and hot basking areas to stay healthy. The UV output of reptile bulbs varies. Some of them provide both UVA and UVB, while others only supply UVA. Check the box labels.

Indoors, you can provide UVB with long reptile fluorescent tubes, reptile mercury vapor bulbs (MVB's), or the new reptile metal halide UVB lamps.

Just like the basking area, the UVB area should be a large zone from the most to least intense. UVB should be at the max under, or right next to, the basking bulb and then taper of to nothing over a large area. The whole body of the tortoise should be warmed and under the UVB light, not just a small spot on the top. The other end of the enclosure should ALWAYS provide a shaded, no UVB, area for the tortoise to retreat to as needed.

fluorescent UVB tube sizes

Long reptile UVB fluorescent tube sizes. T-12 is the oldest size, T-8 was the common size before the new T-5 HO tubes were released. Reptile T-5 HO tubes are stronger and put out twice the light and UVB of the older the T-8 tubes.

Long T-8 UVB tubes (old style)

Zoo Med's ReptiSun fluorescent UVB tubes have been popular for years. They are available as 2.0 UVB, 5.0 UVB, and 10.0 UVB bulbs. For Star tortoises, the 10.0 bulb is better than the weaker 5.0.

Many tortoise keepers are switching from the older T-8 tubes to the newer, stronger T-5 UVB tubes, especially in larger enclosures. Due to their higher UVB output, T-5 tubes can be installed higher above the tortoise.

Long T-5 UVB tubes (new style)

Two brands of the new T-5 HO (high output) UVB tubes for reptiles are available in the U.S. - Zoo Med and Arcadia. Both used to made in the same factory in Germany and were of comparable quality, but after Zoo Med's manufacturing change, the Arcadia T-5 tubes are now considered to be the better ones putting out more UVB.

These T-5 HO UV tubes will not fit in the old style T-8 fixtures. They require T-5 specific fixtures.

1.) Arcadia T-5 tubes (update winter 2011-2012)

2.) Zoo Med T-5 tubes (update Nov 2012) 3.) Zoo Med LED UV hoods (update Apr 2014)

UVB tube fixtures & reflectors

Shop light and strip light fixtures are perfect holders for the long UVB fluorescent bulbs. Always check the size info to see if the fixture is made for the older T-8 tubes or the current T-5 HO tubes.

Using reflectors with the UVB bulb fixtures maximizes the light and UVB output by directing it all into the enclosure. Always check the minimum installation distance on the box to keep the UVB at a safe level for your tortoise. Ideally, use a UVI meter as well to create the appropriate Ferguson UVB zone for your species.

Compact (short) UVB bulbs

Compact reptile UVB bulbs are short fluorescent bulbs that usually, but not always, screw in just like regular light bulbs. They can be straight or coiled (spiral) in shape. For tortoises, long UVB tubes are preferred over these compacts.

Compact UVB bulbs have created a lot of controversy among tortoise hobbyists. Some keepers say there are fine to use when properly installed overhead, while others swear compact bulbs have caused severe eye problems, even blindness, to their tortoises.

a.) Compacts - possible eye damage

b.) Compacts - small UVB zones

c.) Compacts - possible initial UV spikes

d.) Compacts - placement

Mercury vapor UVB bulbs (MVB's)

Just like with the compact fluorescent UVB bulbs, there has been manufacturing problems with MVB's in the past. For example, some MVB's from batches JI, KI, LI produced after Oct 2009 were affected. These defective MVB's emitted abnormally short wavelength UVB radiation and increased the risk of an eye problem called photo-kerato-conjunctivitis. (Source: UV Guide UK)

Several brands of MVB's are on the market, but it's safest to stick with respected, well-known ones. Zoo Med's PowerSuns and Arcadia's lamps are are popular.

a.) MVB's - dimensions

b.) MVB's - fixtures

c.) MVB's - wattage

d.) MVB's - minimum distance

e.) MVB's - don't shake

Metal halide lamps

Metal halide reptile UVB bulbs are new to the market. They provide visible light, heat, UVA, and UVB and are considered to be superior to MVB's. Metal halides' light output is bright and naturalistic. Unfortunately, their beams are narrow and the UVB decays fast. At least currently.

Two U.S. examples of these lamps are the Zoo Med Powersun H.I.D. Metal Halide UVB Lamp and the Exo Terra Sunray. They must be used with metal halide lamp specific fixtures. Dr Frances Baines and others have started testing these bulbs. You can read their findings and recommendations at the Facebook Reptile Lighting group.

Day & night hours

A common recommendation is to keep indoor tortoise enclosure lights on 12-14 hours a day during the summer and 10-12 hours during the winter.

During the day, the enclosure should be warm and brightly lit to simulate daytime. At night, the enclosure should be dark. Ceramic heat emitters (CHE's) and reptile radiant heat panels are great for nighttime heating because they provide no visible light, only heat. See the heating page for info.

Measuring UVB exposure

a.) Length of time per day

How much exposure to UVB do tortoises need? Traditionally, the UVB exposure was measured in time, but published recommendations varied from a few minutes to hours daily. Some examples are below.

For example, Dr Hartmut Wilke, a German biologist and zoo director (Schildkröten, 2009 / Turtles, 2010), suggests an exposure of 10-20 minutes. He feels that too much UV is pointless and only breaks down the initial level of vitamin D3. His recommendation is to shine the UV light for about 20 minutes during the morning activity period and another 10 minutes during the afternoon activity period.

On the other hand, Andy Highfield of Tortoise Trust (Promoting Proper Bone Development, 2003), suggests that spending 3-4 hours outside daily is enough UVB exposure to produce adequate levels of vitamin D3 in tortoises if you live in an area that has native chelonians.

Read also the Tortoise Trust (TT) forum thread titled "How much UVB exposure" [offsite] from August 2011. That thread includes posts from Frances Baines, M.A., VetMB, MRCVS, of Reptile UV Guide UK. Frances Baines is a retired veterinary surgeon and well-known for her research on reptile UV lighting.

In that same TT thread, Andy Highfield writes about tortoises: "In captivity, you are really looking for an acceptable, functional, 'average' figure, which going by all the evidence I have so far, is likely to be in the 150-180 uW/sq cm range for 30-40 minutes a day at basking temperatures in the 30-34C [86-93.2F] range. Basking temperatures are critical, because temperature is part of the process in converting UVB to usable vitamin D3 by activation of sterols in the skin."

b.) UVB intensity per Ferguson zones

The newest way to measure the needed UVB output, especially indoors, is to use a UVI meter and then apply the Ferguson zone for your species. Most tortoise species, including Indian Star tortoises, fall in the zone 3.

For zone 3 open sun baskers, like Star tortoises, use the "sunbeam method" with the maximum UVI reading of 2.9-7.4 in the basking zone. The highest UVB should be only under the basking bulb and must then fade to nothing over a large gradient. Always provide shady spots in the enclosure as a retreat.

Reptile magazine's Jan 2017 article by Dr Baines has a good overview of Ferguson zones and reptile UV lights. See links below.

Solarmeter 6.2 for UVB, Solarmeter 6.5 for UV index

Solarmeter 6.2 for measuring UVB and Solarmeter 6.5 for measuring UV index (UVI).

In the past, model 6.2 was popular, but currently the model 6.5 is considered to be more useful for tortoise keepers. These two meters are now also sold as 6.2R and 6.5R versions with reptile specific charts on the covers (not pictured).

UV meters

You can monitor the intensity and ageing of your UVB lamps with small, handheld devices called UV meters. These meters are also used to install UVB lamps at the proper height to provide the correct amount of UVB based on Ferguson zones.

Solarmeter 6.5 is the most useful one for tortoise hobbyists. This meter is also sold under the Zoo Med label as the Digital UV Index Radiometer (model ST-7) and as the new Solarmeter 6.5R.

The Solarmeter 6.5R model is designed specifically for reptile keepers (R = reptiles). Actually, it's the same meter as model 6.5, but it has the Ferguson zones chart (1-4) for reptiles on the cover instead of the human UVI chart (1-15) of model 6.5.

For info on Solarmeters (models 6.2 and 6.5) and Ferguson zones, along with some outdoor UV measurements, see my UVB & UVI readings page.

UVB & glass

Normal window glass does not transmit UVB. Sunlight through a closed window does not meet tortoises' need for UVB. Even a mesh screen top will filter out some UVB, probably about 30-50% depending on the size of the mesh openings.

You can buy special types of glass or acrylic that allow the transmission of UV radiation, but they are more expensive than regular glass.

There is also a new generation of garden greenhouse films that allow full UVB to pass through. These plastics are especially useful for building outdoor warm up areas for tortoises utilizing polytunnels or small greenhouses.

Links - More info

Links - Articles


Related page: UV readings outdoors (UVB & UVI w. Solarmeters 6.2 & 6.5)

to Top of page


web stats