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Remember that the Red-Eared Sliders are cold blooded animals, they depend on the temperature around them to be able to warm up, and warmth is essential to their health!

First, a few basic facts

Most reptiles require high quality and appropriate lighting to meet a number of different metabolic needs. The only exceptions are certain nocturnal and dense rainforest species. It is not necessarily the case that all of these needs can be accommodated by one single form of lighting. A combination of different lighting systems may be required in some cases.

Under natural conditions, in the wild, many reptiles synthesise their own vitamin D3 from the UV component of sunlight. Vitamin D3 is essential for the effective metabolism of dietary calcium in reptiles. Certain wavelengths in the UV spectrum (290 - 320 nm) react with sterols in the skin to produce pre-vitamin D3. This is in turn converted into vitamin D3 itself, using a process which also depends upon heat. . Carnivorous and omnivorous reptiles get a high proportion of their vitamin D3 requirement from their food, however, plants do not contain D3, cholecalciferol, instead they contain D2, ergocalciferol, which is far less efficient in calcium metabolism than D3. Herbivorous reptiles kept indoors are, therefore, far more dependent upon the quantity and quality of artificial lighting than carnivorous specimens.

If inadequate vitamin D3 is available, the animal will rapidly develop the condition known as MBD or Metabolic Bone Disease. In this condition, bone density suffers and various other serious metabolic problems occur. Symptoms include swellings, lethargy, general weakness and tremors. The shell may also become soft and pliable. MBD remains the number one killer of captive lizards, tortoises and turtles (snakes are less affected as being highly carnivorous they easily obtain their D3 requirement via their prey). To prevent MBD, adequate levels of calcium must be present in the diet, and adequate (but not excessive) quantities of D3 must be provided by means of dietary supplementation or by exposure to adequate levels of UVB lighting. Rapidly growing specimens such as hatchlings are most at risk, although adults too will be affected if maintained in a state of deficiency for long enough. Egg laying females are also at great risk, due to the extra demands egg production places upon their calcium metabolism.

In the tropics the light intensity of the sun at ground level is in the region of 1,000,000 Lux, while even in the rainforest canopy it can exceed 7,000 Lux. By comparison, a 40W incandescent lamp typically produces less than 50 Lux when measured at a distance of only 1 meter! This demonstrates very clearly just how very "dim" even the best illuminated terrarium is compared to nature.

Artificial lamps used in vivaria and terraria fall into two main categories:

  • Incandescent lamps
  • Spotlights/Reflector Lamps

These are standard incandescent lights with a silvered reflector backing to direct the beam. They are more useful as a source of heat than light. They can make excellent basking lamps, however.

Lighting is very important. Lighting does 4 major things for turtles. It helps them raise their body temperature, it dries them off which will prevent fungus, promotes natural shell growth, and tells the animal what time of the year it is. To provide this lighting you will need 2 different types of lights, a heat lamp, and a fluorescent UVB light. Light serves two very important functions for your turtle - heat for basking and UVB radiation for calcium metabolization. If not provided properly both can lead to long-term diseases, poor growth, diseases and worse… The heat lamp can be just ordinary desk lamp with an incandescent bulb in it.
This light is used to provide
white light to the tank and heat in the basking area. The basking (land) area should be at a higher temperature than the water. That can be achieved by using a white light source near the land area that generates heat. While a lot of literature mentions using specific Reptile Basking Lights, normal bulbs (that you use in your light fittings at home) can do the job equally well. Position it over the animals basking spot. The air temperature at the basking spot should get to the mid-80s. If its not, the turtle will think it doesn’t need to bask.
Mount/Place this so that the light focuses on the land area. Ensure that there is no way that the turtles can reach the light source, its wires or topple it over! (this means a distance of atleast 10 inches from the land area!)
Depending on the climate of the place you stay in, a higher wattage bulb might be required in winters. The best way to check this is to start with a 40W or 60W bulb and take the temperature of the land area after every hour. You should be able to maintain land-area temperature in the range of 26.6 oC - 32.2 oC (80 oF-90 oF) even after keeping the bulb lighted for 12-14 hours continuously.
In case you observe the temperature to be constantly bordering on 32oC (90oF), shift to a lower wattage - you don't want a sun-dried turtle!Secondly, you need to get the fluorescent light fixture. These can be standard aquarium fixtures found at most pet stores. Remove the glass cover on it because glass filters 99% of the UVB rays. Remove the bulb too. This bulb needs to be replaced with a reptile bulb. The best brand is Reptisun 5.0. These produce the most UVB possible. The turtle absorbs D3, which is a vital component of the calcium metabolization process, from the light and uses it to process calcium. In their natural habitats turtles are exposed to direct sunlight, in which they bask. Turtles in captivity don't receive this direct sunlight and this can lead to shell diseases, malformations, etc. To avoid this the tank needs to be fitted with a special light that can serve as an artificial source of UV rays. Additionally turtles need to be given Vitamin D3 supplements in their diets, but for that refer to the section on Feeding. Merely keeping the tank next to a window in sunlight will not help as window/tank glass filters out nearly 93-95% of the UV rays in sunlight. Internationally 'full-spectrum' fluorescent reptile lights (ReptiSun, VitaLite, etc.) are available that produce upto 5% of the UVB spectrum. These resemble conventional tube-lights that we have in our houses, but have special coatings that last upto an year. They need to be installed at a distance of approximate 8-12 inches from the basking area. Calcium is essential to form proper bones and shell. UVA is also produced from Reptisun bulbs. UVA provides psychological benefits for reptiles. The bulbs stop producing UVB after about a year so replace after that. Once you have the bulb installed to the fixture, position the whole thing over the basking spot, too. It is essential that these cool white lights be installed on the same side as the basking lamp. This is because turtles prefer to come out of the water and bask in warm light, and would get maximum exposure to UVB at that time. In the absence of this UVB light, install CFL's or normal tube-lights to create a cool, low-electricity consumption light source for the tank. Now, you may be thinking, what is a basking spot? Well, a basking spot is simply a place where a turtle can get out of the water, rest and dry off. It is important that turtle can dry his entire body off. A basking spot can be made from almost anything, rocks, plexi-glass, driftwood, cork, etc. Be creative. Do not use Styrofoam or anything that can break off into little pieces. The turtle may swallow the little pieces. If using rocks, make sure not to stack them too high or they may topple. Be sure they can support the turtle.You need to keep you lights turned on for atleast 10-12 hour stretches daily. These can be varied if you want to mimic the seasons.
As for giving the turtles UVB exposure there is just one way - direct sunlight!
You can buy a timer to make this easier.

I recommend either of the following easily available light bulbs:
OPTION 1 : Bulbs with a white paint/coating on the inside (e.g., Phillips SuperLux)
OPTION 2 : Spotlight bulbs, these are less round in shape and have a silvery coating on the inside to focus light on a specific area (e.g., Phillips SpotLine)

The importance of good lighting

Turtles depend on full-spectrum lighting, which is an artificial illumination that will sustain their day/night cycle, and help them to process the nutrients of the food you provide. A group of vitamins, specially D3 are absorbed into the turtle's body through direct exposure to UVA or UVB lights. This absorption encourages proper bone formation and shell health.

Full-spectrum lights

At your local pet shop they should have a variety of full-spectrum lights specially designed for reptiles. I recommend the Reptisun 5.0 or Vitalights. Remember to add a basking area to your aquarium so that the turtle can get out of the water, and benefit better from your light.

No lamp is truly "full spectrum", but some get closer to this ideal than others. Today, there are a wide range of high quality fluorescent tubes available which are specifically designed for use with reptiles. Some of these, are, however, better than others and the intensity and quality of light emitted does vary considerably from brand to brand and from model to model. Note that fluorescent tubes do not provide any heat output and that a separate, incandescent, basking lamp is always required in addition. There are three main properties which are of special interest to reptile keepers, and I would rate them in the following order of importance:

  • UVB output - critical to vitamin D3 synthesis and the calcium metabolism;
  • Color temperature - nothing to do with heat, but rather the color from 'warm' red to 'cold' blue expressed in degrees Kelvin. Daylight at noon is typically estimated at 5,500 K. At the tropics, or in a desert, the color temperature can reach 6,500 K.
  • UVA output - many reptiles are believed to be able to see into the UVA range (320-400 nm), and this is likely to have a profound effect upon behaviour, and specifically, how they visualise food items.
  • Color Rendering Index: Color rendering is the degree to which a light source shows the true colors of the objects it illuminates. This is measured on a color rendering index, rated from 0-100. A normal fluorescent lamp, for example, rates 54 on the CRI scale. High quality fluorescent lamps designed for reptile use will rate 80-90 on the same scale. Color rendering is very important as many reptiles rely upon color signals for reproductive and feeding purposes.

The combination of sufficient UVA content and a 'natural' >5,500°K color temperature is most probably the reason why so many keepers report a marked improvement in activity patterns and feeding when high quality full spectrum lighting systems are utilized in enclosures. In addition to the quality of the lamp, its proximity to the animal, its output intensity and duration of use are also critical.

The illumination intensity of tubes is primarily dependent upon their size. A 24" tube producers less than half the light output of a 48" tube. Do not expect to be able to provide adequate levels of lighting in a large vivaria using a single small tube. One keeper found that in order to provide a satisfactory level of lighting for a 10' X 5' indoor enclosure eighteen 48" 40W full spectrum fittings were required. Our own 6' X 2' terraria for juvenile Mediterranean tortoises have at least two 48" fittings. One useful tip: fittings purchased from specialist suppliers can be very expensive. Full spectrum tubes work equally well in standard household or industrial fluorescent fittings which can be obtained from electrical and hardware suppliers at considerable discounts.
When installing full spectrum or UVB producing tubes, it is absolutely critical that nothing is placed between the envelope of the tube and the recipient animal. UVB is greatly attenuated by glass, plastic and even fine mesh (the tube envelope itself is a special type of glass which does permit UV transmission). The amount of UVB received also diminishes extremely quickly with distance. It is generally recommended that such tubes be no further than 18" (46 cm) away from the subject. At greater distances than this, the amount of UVB actually received will be minimal. For reptiles with very high UVB requirement, such as desert species, tubes should be placed as close as 10-12" (25-30 cm) above the basking site - although the new 'UV-Heat' type lamps are probably more suited overall to this application (see below). It may be necessary to install fittings on a sub-framework located within the terrarium in order to achieve this. Tubes also have a very limited life. Most will require changing every at least 12 months in order to guarantee continued UVB output. There is evidence that some tubes fail to produce advertised levels of UV-B after only 6 months of use. Although there may be no visible deterioration in the performance of the tube, there is ample evidence that the invisible UV content decays rapidly as the tube ages. It is a good idea to place a small adhesive label near each fitting with the date the tube was last changed clearly marked.
Full spectrum UVB tubes produced for reptile use are often classified according to their percentage UVB output. Tubes are available offering from 2% UVB to 8% UVB. The most popular tubes offer 3% or 5% UVB. In the vast majority of cases the 3% tubes are perfectly adequate, provided they are correctly sited, changed regularly, and a sufficient number of hours exposure permitted. For a 3-5% tube, 10-12 hours daily has proved a satisfactory level of exposure for most species. Concerns have been expressed about the safety of tubes with outputs greater than 5% - in particular, there may be a possibility of eye damage occurring with some tubes in some situations.

Do NOT use black lights

Black lights emit a very dark purple beam and you have probably seen them being used in plants. These lights are NOT recommended for turtles, due to tests show that turtles will damage its vision due to the hight intensity of the beam. There have been cases reported of turtles that have been totally blinded by these lights. Some types of black light are used for special effects in discotheques. This type of lamp is of no use to reptiles. Other types are used for various industrial purposes, for example, in sterilizers. This type of lamp can be positively dangerous to living creatures, including humans, as they emit UV-C which can cause skin cancer and eye-damage. The only "black light" which is of any use to reptiles for D3 synthesis are those specified as "BL" types. These emit both UV-A and UV-B radiation at a relatively high level. They have been used successfully with many species of reptile, but high output UV-B full spectrum types are generally preferable. Black lights tend to emit an unpleasant violet glow, and provide no "daylight" frequency light whatsoever. They should therefore only be used in combination with a true full spectrum tube. As FS tubes with sufficiently high UV-A and UV-B outputs are readily available, black lights are now largely redundant. For general use, they are not recommended. There may be highly specialized applications where their use is justified. An alternative "black light" is now on the market aimed at simulating moonlight for nocturnal reptiles. This should in no way be confused with the true UV black lights described above.


This is simply the duration of the period in which the light stays on and off. Do you wish to hibernate your turtle, you have to mimic the natural seasons, provide more light and for longer hours in the summer.

Reptile Basking Lights (neodymium lamps)

Above: Don't be fooled! This lamp emits NO UV-B and will do nothing to prevent MBD. An ordinary domestic bulb is just as good, and a lot cheaper. This type of lamp should not be confused with genuine 'full spectrum' lamps.

These lamps are sometimes misleadingly, in my opinion, described as "full spectrum". In fact they are ordinary incandescent lamps with a built-in blue filter which serves only to change the color balance of the illumination. They emit no useful UV and must not be relied upon as a sole source of lighting in reptile enclosures.

None of the above lamps emits useful quantities of UV-B or UV-A. They are therefore of no use whatever in promoting vitamin D3 synthesis.

Infra-Red Reflector Lamps

Usually only available in high powers, e.g., 150-250 watts. They do not offer a great advantage over standard spot lamps and their red glow is particularly unnatural. Not generally recommended for reptile use.

UV-B Heat Lamps (Self-Ballasted Mercury Vapor)

It is not often that a genuine revolutionary product comes along – but these lamps have proved a major hit with lizard keepers, and now tortoise and turtle keepers are also reporting excellent results. Superficially, they appear similar to a regular incandescent reflector lamp, but unlike a regular incandescent spot lamp, they also emit very significant levels of essential UV-B. The color of the light they emit is also much whiter, and brighter than a normal spot basking lamp. Not only that, but they also emit a very useful amount of heat. The levels of UV-B and UV-A produced by these lamps is extremely impressive. At 30 cm, it approximates that at midday in the Mediterranean. At 60 cm, it produces far more than even the best UV-B fluorescent tubes can manage at half the distance. The lifespan of these lamps is also excellent, with very useful levels of UV-B being produced even after 3,000 hours of use (by this time, tubes are virtually dead in terms of UV-B production). We have had these lamps on trial at the Tortoise Trust for the past year – and we are highly impressed with their performance. We are so impressed that we are replacing our old tube fixtures with them completely. They appear expensive at first sight (from $40-$60 upwards each), but given their excellent performance and longevity, are actually cheaper in the long run than UV-B fluorescent tubes. As the levels of UV-B and radiant heat produced are extremely high, you must install them carefully and follow the maker’s instructions to the letter. A heat resistant lamp holder is essential, for example. Two sizes are generally available, 100W and 160W in spot or flood. For general use, we recommend the flood models. Larger 300W versions may also be available from some suppliers.

These are the only readily available lamps that combine appropriate radiant heat output with high quality visible spectrum and UV-A/UV-B output. As such, they offer a truly excellent option for tortoise and turtle keepers. The only drawback is limited supplies, especially in some areas. Initially, only one company offered these lamps, but slowly other companies are also bringing similar products to the market. Check a specialty reptile magazine for the latest on availability and prices.

Despite advances in lamp design, there is still no substitute for natural sunlight. Wherever possible, all diurnal species should be given access to unfiltered sunlight. Use outdoor pens as much as possible. Even the very best artificial light source literally pales into insignificance compared to the sun. Bearing in mind concerns about premature UVB  flourescent lamp failure, it is the view of the Tortoise Trust that tubes alone should not be relied upon exclusively to provide vitamin D3. It is our opinion that it is far safer to continue to provide a high quality combined calcium-D3 supplement orally, even where full spectrum tubes are employed. Full spectrum tubes do offer many other advantages apart from stimulating D3 production, however, and we therefore recommend that they should be installed in all indoor enclosures except where 'UV-Heat' type lamps are available. Where 'UV-Heat' lamps are used, however, it is our view that oral D3 should be reduced to once or twice per week, and a plain calcium carbonate (phosphorus-free) supplement used instead on a daily basis.



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Site Created: 1/8/2002, Last modified: 12/7/2003 by Petra Grujic