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You are browsing the archive for light.

Profile photo of Stacy

by Stacy

Do I need a light?

February 18, 2014 in Crabitat

This was originally posted on All Things Crabby: http://www.allthingscrabby.com/blog/index.php/2009/10/25/do-my-crabs-need-a-light?blog=3

Yes they do.

Light and proper food fuels a hermit crabs metabolism. A hermit crab’s metabolism enables them to adjustment to their surrounding environment. Hermit crabs require a normal cycle of day and night to maintain their metabolic functions. Along with a nutritious, balanced diet. A cycle of 12 hours light and 12 hours night is commonly recommended and used. With overhead lights you will notice that your crabs will be more active during the day. We’ve always been told that because crabs are nocturnal, they are not active during the day. Try turning a light on them and you will see how false that is. Hermit crabs are primarily nocturnal but not exclusively.

Your overhead light can also be your heat source. I recommend you use a set up with a day bulb and night bulb. You can purchase a bi light hood that will accommodate two bulbs that are controlled with two switches. This means you can buy a couple timers and set your lights on a timed cycle to come off and on as needed. The wattage of the bulbs will be determine by the size of your tank and if you are using the bulbs for your heat source. If you don’t need the bulbs for warmth, go with a very low wattage. You are looking for incandescent bulbs that provide UVA rays. These are bulbs sold for reptiles.

Even molting crabs should be kept on a normal cycle. This flies directly in the face of advice we have been given for several years. Molting is a metabolic process. Now if you consider molting in the wild, a crab simply digs down and molts. It doesn’t go into a dark cave or den, then dig down and molt. When the crab digs down, it is obviously in the dark but there is no reason to deny the crab of light pre or post molt.

Sue Latell of Coenobita Research has been conducting a light study and continues to research the benefits and affects of light cycles on hermit crabs. This information has been derived from her current research articles or conveyed to me directly during our discussions on hermit crab care.

The relationship between light, food and a hermit crab’s metabolism and how it plays a role in environmental adaptation, is exclusively the result of Sue Latell’s many hours of research and study. Sue’s ability to decipher and apply research papers and her consultations with experts in the field, have revealed some large flaws in our previous methods of crab care. It is always an effort to change the popular, common methods but in the case of hermit crab care, it is vitally necessary to improve the quality of life we provide to our hermit crabs.

Profile photo of Stacy

by Stacy

Can I Use A Light To Keep Them Warm?

October 16, 2012 in General

Compiled by Vanessa and Marie (aka ladybug15057)

There has been a lot of false information when it comes to hermit crab care over the years. One of the biggest known factors of land hermit crab deaths is dehydration from the use of desk lamps with a common household bulb, coupled with wood shavings as substrate in a plastic ‘kritter keeper’ with vented lid. Before Under Tank Heaters
or thermostats were made available to the public, many hermit crab owners were advised by pet stores to leave the desk lamp on overnight to help keep the chill of dropping temperature at bay. Desk lamps have been proven unsuccessful at meeting the needs of land hermit crabs as a primary heat source, resulting in fatality, especially when coupled with wood shavings as a substrate in an enclosure where any humidity escapes through the vented lid.

If you use an Under Tank Heater which covers half of the dimensions of the base of your tank as the primary heat source, you may not need the lamp as a heat source. You may be still want to illuminate the tank overnight (with a moon glow bulb with a rare phosphorus coating) so that you can watch the activity in the food dish or stare wide-eyed during a seashell swap. The only light recommended for night viewing is a moonlight-simulating globe (or moon glow bulb)that is coated with rare earth black phosphors that simulate the glow of the moon. Perfect for our hermit crabs who are more relaxed eating, climbing and swapping shells beneath the gentle light, which gently illuminates your crabitat. You will be amazed how much more active they will be with the extra warmth. It is my personal choice to use bulbs no higher than 40 watt, with 25W for a small crabitat. Others have chosen higher wattages to warm their larger (100 and 120 Gallon tanks. It is important to take the size of your crabitat, substrate type and other factors before deciding upon your lighting needs. It is very important to monitor the substrate temperature as well as the humidity level of the crabitat.

Some bulbs are of the ‘Edison Screw’ type, and require a lamp such as Zoo Med Deluxe Porcelain Clamp Lamp
or a Reptile Hood/Strip fitted for edison screw bulbs. Both are used over the tank, with the glass between the light and hermit crabs. A 15 Watt bulb can be used for lighting purposes, however the ambient (air) temperature may rise 1-2 degrees. With higher wattages you may notice a problem with keeping the humidity within the 75-78% range. Many hermit crab owners have chosen to add a reptile water dish or have installed drip systems, timed misters, or waterfalls to keep the humidity level from dropping.

It is important to keep a close eye on both the humidity and temperature within your hermit crab’s enclosure, and to provide an environment that will put your hermit crabs at ease as well as keep them happy and healthy. Investing in items such as under tank heaters, moon glow bulbs, hoods and possibly thermostat or rheostat to regulate conditions and your hermit crabs will have a higher chance of survival when Summer leaves us and cooler days approach. Left without adequate heating and humidity would usually result in lowered activity. hibernation and perhaps fatality. While a desk lamp may seem an economical solution, I’m sure you will agree that the death of a loved hermit crab is too high a price to pay.

For some ideas on the different types of lights you can use check out our Methods for heating your hermit crab tank article.

Note: As with heat from an under tank heater, it is highly recommended that a thermostat is used.

Profile photo of Stacy

by Stacy

Methods for heating your crabitat

September 25, 2012 in Caresheets

Compilation of information by Vanessa Pike-Russell and Stacy Griffith

To keep your hermit crabs healthy and happy their environment should be kept in optimum temperature and humidity levels. If you are not able to keep the environment stable then your crabs will weaken and become stressed which will lead to death. Hermit crabs are cold blooded creatures and must have a warmish and cooler side to their substrate. If your temperature falls below 72oF on a frequent basis you need a reliable and safe method for heating your crabitat. Whatever type of under tank heater or other heating method you use, it is STRONGLY recommended that you buy a temperature control device such as a thermostat or rheostat. See some examples at the bottom of this page.

Sources of heating suitable for crabariums/crabitats are:
• Under tank heat mats or strips
• Overhead lights
• Heating cables

Note: Heat rocks are not considered safe for hermit crabs!

Here are some examples of suitable products you can use to heat your crabitat. Click the links to read more product info


1. Under-tank heaters


There are many types of under-tank heaters used with reptiles but you need to make sure your crabs do not overheat. The UTH should cover approximately 1/2 of the tanks outside floor. They are sold in a variety of sizes based on your tank size. The best kind are those that keep the temperature stable between 72 (cool side) and 80 degrees F (22-26.67oC) warmer side. Hermit crabs are cold blooded creatures and must have a warmish and cooler side to their substrate.
UTHs can be used on plastic tanks however, plastic tanks are not recommended for use as permanent crabitat!!

Eurorep habistat heat mat diagram

Eurorep habistat heat mat diagram




Reptile heat strip

Reptile heat strip




Heat Strips are manufactured in the same way as mats. They are made narrower and are generally used to heat small boxes and the cages used for housing juvenile snakes and some other species. The principles of use are the same as those for mats and the same precautions should be exercised. In small enclosures the heat build up can be very quick. The temperature should be adequately monitored and controlled with a HabiStat thermostat.
Heat Strips are available in multiple sizes.

Eurorep heat strip

Eurorep heat strip




2. Lights


Lights come in a variety of shapes and sizes. Below are just the common styles to give you some ideas of what is available. Because hermit crabs require a regular cycle of day/night it makes sense to use overhead lights that emit heat. This fills two needs with one item. Reptile bulbs come in day glo and moon glo (with a rare black phosphorus coating) so that you can have warmth at night, which is necessary. The wattage of bulb needed depends on your tank size.

Clamp lights
You will need to switch bulbs from day glo to moon glo or purchase two lamps.


Multi fixture hoods – Available in a variety of lengths

Bi Light Fixture

Pack your reptile’s daytime and nighttime heating all under one hood with this handy light fixture. Reptile terrarium heating and lighting has never been easier. The Bi-Light 2 Reptile Hood Lighting Fixture features two single high-heat ceramic sockets on separate switches and separate power cords and accommodates two incandescent bulbs.

Tri Light Incandescent Fixture

Tri Light

Tri Light




These are more difficult to find now.

Designed exclusively for terrariums, the Tri-Light fixtures feature high-heat porcelain sockets built to withstand the intense heat that is emitted from high-wattage incandescent lamps. A single socket and a double socket on separate switches and cords hold three incandescent lamps up to 150 watts each. The lamps can be plugged into individual timers for both day and night cycling. Available in 30″ size.(6″L x 31″W x 4″H)

Tri Light Combo Fixture

A combination fluorescent and incandescent light fixture designed to maximize the benefits of both types of lamps.
This allows for the use of a full-spectrum, UV-emitting fluorescent lamp along with incandescent full-spectrum daylight/heat lamps and/or incandescent nocturnal/heat lamps. The fixture contains special heat-resistant ceramic sockets for the incandescent lamps and is designed to direct light and heat down into the terrarium. With the combo-light, hobbyists can create an ideal lighting environment for their terrariums.

3. Heat Cable

Greenhouse cable can be a heating alternative for people who are unable or uncomfortable with other sources of heat. Using GHC, however, requires some additional precautions to protect the crabs and yourself. Only use enough cable to cover 2/3 of your tank floor. This allows your crabs to seek out temperature zones for resting and molting underground. Place cable in tank and secure with small strips of heat resistant tape.

Purchase a reptile mat to lay over the cable. This works best if the reptile mat is the same size of your tank floor. Cut a small hole in the corner of your reptile mat and thread the power cord through the hole.
The cord should then be threaded through a piece of PVC pipe that has been cut to fit the height of your tank.
The thermostat should be placed under the reptile mat as well. Crabs can and will cut through rubber and other types of cable insulation. Every part of it must be protected from the crabs.
Once this setup is in place, lay your substrate out on top of the reptile mat and continue with your setup as you normally would.

Check substrate frequently over the next few weeks to confirm that your reptile mat is working correctly
These heating cables speed seedling germination and growth with gentle bottom heat allowing you to get a head start on the growing season. They have a built-in thermostat that automatically activates the heating element if the soil temperature drops below 70 F which is the optimal root zone temperature for most seedlings and starts. Each heating cable includes installation instructions and helpful tips. 110/120 volt electricity required.


Thermostats and Rheostats

Should I use a Rheostat (dimmer) or a Thermostat?

Don’t forget the bulbs!
The wattage and type of bulb you need will vary by fixture and by the size of your crabitat. Day bulbs and night bulbs are needed to maintain a natural light cycle which is vital to successful molting. ARTICLE??