Project talk:Aquarium Edge Illumination
From CoMakingSpace Wiki
LED Strips Alternatives
Here you can get cheaper and waterproof LED strips. If you need a receipt then eBay would be another (less) cheap option. (Patrick)
Driver Circuit
What do you want to control with the Arduino? Just the brightness, or also automatic on/off time during the day? For just regulating brightness these things look rather easy to use. (Patrick)
ESP 8266
In case the arduino is needed for some time control, etc, you could also check out this according to sources (heise), it comes with an ESP8266, which can easily run your own software...