These Black Light Tubes are the disco lights that make your shirt glow very white, they are also used for detecting counterfeit notes
Blacklight blue is harmless UV and these lamps are usually used for fun
They are essentially the same as a standard fluorescent tube they just have a different gas filling and are a purple colour rather than white!
They are available up to 4ft in length and they run in ordinary fluorescent fittings
Blacklight blue tubes are often mistaken for another type of UV Tube which is actually germicidal, this type of lamp usually found in your pond filter. Make sure you don’t get them mixed up!