Indoor lighting for Ping

[telamont]

I have a T5 fixture that holds 4 bulbs I am going to sit on my 20 gallon long terrarium I made. The light has legs so it sits a little above the tank. Can anyone tell me how far away they grow pings under T5's? How far should my light be from my pings. Also, where and what kind of bulbs do people use in the fixtures? Can they be purchased at a local hardware store. My fixture is from an aquarium so it has blue and white light I was thinking of experimenting but was hoping to hear what other people had to say. Thanks! I don't want to kill any of my beautiful butterworts.