UVA and UVB for Hermit Crabs

Post by **JediMasterThrash** » Tue Sep 19, 2006 1:03 pm

Here's a copy of my post on HCA:viewtopic.php?t=40222&highlight=UVA: Here's some info about UVA: http://www.emaxhealth.com/66/7215.html UVA is mostly transmitted through glass and screens (and is not blocked by normal sunscreen and it penetrates deeper into the skin and causes aging and melanoma). Our crabs are probably a small amount of natural UVA even indoors in crabariums. A UVA light on a crabitat will provide extra. Reptiles see in the UVA range, so they have increased activity when exposed to UVA. UVB: Here's my source on the UVB-info http://www.uvguide.co.uk/index.htm Basically: chicken wire (very coarse mesh): Reduces UVB by 7% mesh: Reduces UVB by 15-30% flyscreen (very fine mesh): Reduces UVB by 50% Aquarium glass: Reduces UVB by 98.5% Plexiglass acryllic: Reduces UVB by 20-40% Combination of house windows and aquarium means that the hermit crabs are getting absolutely 0% natural UVB. If you place a UVB light ontop of a glass or plastic lid, likely only 2% of the UVB is reaching the crabs. Reptiles use UVB to synthesis Vitamin D3 So, in order to effectively use a UV-light, you need to have the light over a screen or open-portion of the top of your crabarium. As for lights reducing humidity, it's not something you have to worry about if done right. The heat from lights increases the saturation point of the air, so for a given amount of water vapor in the air, the relative humidity will decrease. However, a properly setup crabitat should have good pools of water and a moist/sandcastle substrate. The radiation from the light will evaporate more water from the pools and surface, increasing relative humidity. The hotter air will increase air pressure, so the air will try to escape out of the tank, rising out of gaps in the lid. You'll simply have to reduce the gaps in the lid. I always have my tank lid proped open about 15-degrees (PI/12 radians), and the relative humidity stays 75-80%. Of course it helps that I have two tropicaire humidifiers running to keep moist air coming in. But for my ISO, I just prop the lid or de-prop the lid as necessary to regulate the humidity. The only thing you'll have to do is refill the water pools more often, since they'll evaporate faster, and maybe occasionally mist the substrate (or poor small amounts of water down the sides) to keep the substrate moist. 15w fluorescent UV-lights add a negligible amount of heat. You should put them on timers so that the only come on during daylight hours so as to keep proper day/night cycles for your crabs. Some crabs will only come out at night. But I've always got a number of crabs that enjoy basking. They will climb up and get as close to the light as they can and sit there all day. And on top of it all, crabs need higher temperatures that most people's houses provide, and overhead lighting (in my opinion) is the best way to provide temperature increases. Moonglo/nightglo bulbs can provide 24/7 heat, and can be found in 15 and 25w packages so as not to overheat/overevaporate the tank. And just because I'm trying to set a guinness book of world records here or something, I'd like to mention that my original pair of 25w moonglos are still running! They've been on continuous for 24,500 hours now! They were only rated for like 2000. For heat, it's fine to go through the glass. Some people have had their glass lids crack from the heat, but mine hasn't yet. Keeping the glass lid over the tank also helps prevent moisture from escaping. However, you'll need to have the UV light over a mesh or open part. The hood should provide enough enclosure so as to prevent much air from escaping.

Willow · Post by **Willow** » Tue Sep 19, 2006 2:44 pm

I have my UVA/UVB light actually rigged inside the tank. I'll post a pic sometime. I don't think it will be harmful to them, at least no more harmful than having a waterfall, water filter, or other corded electric fixture. I'll slip some airline tubing around the cord if it becomes a problem, but there's no pinches in it yet.

newhermiemami · Post by **newhermiemami** » Wed Sep 20, 2006 12:20 pm

I have been hashing these things over in my mind for quite some time, JMT. I want to use the lights for heat and for the UV they provide. I'm planning on getting that 55gal as soon as the darn store gets them in. My big question has been though, what kind of top do I want? I have finally decided that I want to go with a hood with the light fixtures. I think the hood lights take the long tube light bulbs though and I'm not sure if I can get the UV lights to fit. I'm assuming that I can though since I've seen some bulbs like that in the reptile dept. What do you think? I figure it would be better b/c the light would be inside and not blocked by anything so they would get the heat and UV and the hood would keep it closed enough as to not have a big problem with evaporation.

Froggz37 · Post by **Froggz37** » Wed Sep 20, 2006 5:00 pm

I've been using incandesent lights on my crabs tank since I started crabbing. I love how it provides warmth, uv rays, and a day night cycle since each bulb has its own cord and switch. My setup was a combo deal for the ESU tri-light and hinged screen top. I have press n seal on the front part of the screen to keep in the moisture, and the lights themselves are over the screen only. I also have crabs, mostly ruggies and viols that sit as high as they can in the light for most of the day.

Willow · Post by **Willow** » Thu Sep 21, 2006 4:48 pm

Froggz37---do your incandescent lights emit UVB, or just UVA? If they are UVB lights, where did you get them? I ask because the only UVB incandescent bulbs I could find were $50 each, but I really wanted some for my tortoises. The UVA/UVB lights I have now for the hermies and the tortoises are fluorescent. I had some spare aquarium light fixtures that I put them in.

Post by **JediMasterThrash** » Fri Sep 22, 2006 6:47 am

Re-reading my original post, I don't think I explored the Plexiglass alternative enough.Using Plexiglass/Acryllic instead of glass for your lid will provide 60-80% UVB transmission, so it is a good alternative.Especially if you have a tank with a weird lid that you can't easily get a "hood" for. Like my 92g corner tank. The glass lid is shaped like a baseball diamond with a curved opening. So I can't make any hood fixture fit.There are several places on-line that you can get plexiglass made-to-order, so it might be possible to get a plexiglass lid special made for your tank, even if the tank is a regular glass tank.

Guest · Post by **Guest** » Fri Sep 22, 2006 8:43 am

My tank sits in front of my window, which gets the sun in the afternoon. I have an aquarium & a glass lid, do you think that they are getting enough UVA & UVB, or should I add a light as well?

newhermiemami · Post by **newhermiemami** » Fri Sep 22, 2006 10:29 am

Glass blocks the UVB rays. quote:Combination of house windows and aquarium means that the hermit crabs are getting absolutely 0% natural UVB. I havent really seen that its def a requirement but untill I see that its been proven that its not required I want to still provide it. Most of what I've read says its not 100% sure if hermies have to have it but its thought that they use the UV rays to help absorb some vitamins. JMT is our resident genius on all things crawly and creepy so maybe she could clear that up for us both. lol. I use the lights also for heat. My UTH just doesnt cut it. As a matter of fact I'm thinking about not even getting one for my 55. Ive thought about how I can insulate the bottom of the tank under the glass so that the heat would not excape from the bottom and in turn would warm the ee. I dont know how practical this is... Opinions welcome!!

Post by **JediMasterThrash** » Sat Sep 23, 2006 5:42 am

She?As far as I can tell, it's still unknown if hermit crabs benefit from UVB at all. All the research just shows that Humans and Repitiles use UVB to synthesize vitamin D3.However, I did find one article that showed that crustaceans increase their pigments with higher UVB. So you might get stronger colors on your crabs.I think insulating the bottom of the tank would be a good idea. You can probably just put a layer of styrofoam under the tank. The crabs expect to cool off a big when they crawl undergrown, but it depends on how cool your house is.I actually think crabs should have a bit more daily variation in temp and humidity. We should probably have at least two sets of heat lights, and raise the temp to 85 in the day and drop it to 75 at night. Similarly, our relative humidity should go up to 85 in the day and drop to 70 at night.It's seems odd, since we've been so used to saying we need a perfectly stable crabitat, and that wild fluctuations in temp and humidity lead to stress deaths. But I think this needs to be explored more, for the simple reason that their natural environment provides 10-20o/% daily variances for night and day. RH will even drop down to 60 or 55% during the night in winter, and may still rise to 92% on a sunny day near the beach.

TheGreyRonin · Post by **TheGreyRonin** » Sat Sep 23, 2006 4:27 pm

My tank temperatures fluctuate naturally with my house temperature, usually between 86 and 74 degrees depending on the season, and my humidity does right along with it. Except for the unfortunate incident last November, my crabs seem to thrive better with the changing temps/humidity than they do when I micromanage it constantly. Just my two cents' worth, but this is the first time I've seen it brought up.