Correct lighting for OFBT's

[Barry]

I use supplementary lighting in my viv since it doesn't gets very little natural light. The current setup is an Arcadia 24" T8 "Natural sun" tube which gives out 2% UVb and 10% UVa, plus a small heatmat , together producing a temp of 20-23ºC.
I have noticed that some of the toads lose their vivid colour under this lighting - turning dark brown/black. Removing them to an unlit tank restores the colour within an hour. Putting them back into the viv darkens them within the hour.
I realise that colour variation occurs to some extent naturally as a reaction to surroundings and whilst shedding and perhaps when stressed but health , feeding, temp and humidity are all OK. The substate (moss) is light in colour so I'm sure it's a lighting issue.
Most of the books say that artificial lighting isn't required for FBT's but I wonder about this for a diurnal species that is said to bask. Surely an amount of UVa/b is required, but at what level?
I have tried to reduce the light output by placing a sheet of white paper between the tube and wire mesh lid, the light output is reduced by approx. 50% but the toads are still quite a lot darker than I'd like.
Any suggestions?

Barry

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[cobra1264]

First things first is the bulb your using for reptiles? If so get rid of it the mercury vapor in the reptile ones can burn any frogs eyes. Use a fish tank 5,100k pant bulb. I learned this the hard way when a coworker who is a biology major saw I was buying a reptile cfl and lectured me on the risks. Secondly if its stronger then 40W it can hurt their eyes for the UVB and UVA and if its a heat bulb beyond 40W you can burn their flesh. It's a lot to consider but use bulbs meant for fresh water fish and stay away from reptile and salt water bulbs their extremely bright on light out put and for heat use incandescent 25W fish bulbs they put out up to 90F at close range in first 3inches

[Barry]

Ok so a few months on and I've still got the same thing happening. I've used a wide range of bulbs including LED's, tubes for fish and currently the a Dulux Biovital 24W tube 
which is 5800 kelvin so is very close to natural daylight. I've tried all the lights at varying distances and through the mesh screen - still 4 out of 5 of my toads go very dark - yet move them to an unlit,unheated tank and they are back to the vivid colour within hours.
Health, appetite ,pooing, cleanliness are all good and they shed occasionally.
So I'm really stuck for the cause!

[privet01]

As far as lighting, I agree with Cobra. Which I interpret as "you don't need a bright light and you especially don't need a light that put out or adds heat to the viv.

One of my FBT's was very dark when I got it, and I noticed back when I was experimenting with different types/sources of water that alkalinity seemed to make the biggest difference. If I used spring water or distilled water then he'd green up. If I used tap water, then he'd get dark again. The tap was had sat for several days to dechlorinate itself. However, I knew that our tap water was definitely on the alkaline side as many municipal water supplies are around my area. The spring water I purchased was slightly acidic and the distilled water is neutral ph. So I always attributed the dark color to the ph of the water, though I've never seen anything about it from a knowledgeable source.

But if you've got hot bulbs or lots of uv shining down on them and nowhere for them to escape from it, that's just as good an assumption as the ph.