Scareisburg you could use some Florescent dye, like I got off of eBay for use in my lab glass, to color your water.
The listing claims “Each vial will vividly color up to 2 LITERS of tap water!!”
Based on my use of the product you could probably color between one and two gallons of water and still get a nice glow. For a 12 oz beaker I only needed an eye dropper full to get a nice glow.
The seller’s last sale is listed here. There aren’t any currently on sale but you could contact the seller to see when his next auction will be.
http://cgi.ebay.com/ws/eBayISAPI.dll...tem=5645200757