How far should a uvb light be in a 20 gallon tank?

[Nina712]

If you have the tube inside can it be too close?

 

[SHBailey]

It depends on what type it is. Most of them need to be at least 6 inches away from the reptile, but check the manufacturer's instructions on the package. It should tell you the minimum distance.

 

[kingofnobbys]

Refer to the graphs in this
viewtopic.php?f=34&t=235611

and you can easily work out the correct distance from the bottom of the UV tube or UVB globe to the basking spot
> if it's naked (no reflector hood or dome)
> if it's in a reflector dome or hood)
> if it's ontop a mesh lid
> if it's under the mesh lid
... guidance aim for about 180-200 microW UVB / sq.cm @ the basking spot
and about 100 microW UVB / sq.cm elsewhere

note the estimates for UVB tubes not give (ie 5%UVB , 10%UVB , 14%UVB) are easily estimated as the change in UVB wattage is linear.