Clamp on lights?

[Sillyfishies]

Hey I have a 26 gallon bowfront I want to turn into a low to med light planted tank. I decided to use clamp on lights. What type of bulbs would I have to put on em, as this is a 20" tall tank (I think. Ill edit once I check in a sec). Thanks for the answers

 

[Sillyfishies]

Ya it's a 20" tall tank. Will that cause any major problems?