Tank light glows when it is switched off

[KerriPaul]

I have noticed that when I switch my tank light off, a while later in a darkened room the night noticably glows giving a 'moonlit' effect to the tank.

If I unplug it completely the glow goes, but returns when I plug it in again.

Anyone know the cause and if it is something I should be concerned about?

To be honest the moonlit effect is quite nice

 

[The-Wolf]

how old is the tube?
have you tried using a different starter unit?

 

[KerriPaul]

Its quite a new ultra sun tube. I am suspicous that the in line switch on the mains lead may have a very small gap and be 'leaking'. Very odd