They are hard to find and aren't particularly active. They need a sand bed at least as deep as them and you will rarely see them except a flash during feeding time and peeking out when they are comfortable. If you like the spearer aspect then I would suggest P. ciliata, which can be held in a 20 gallon and burrow under rocks. They are much more active and come out and interact, but are also spearers. They get about 4" long and can be Bright yellow or any number of other patterns and colors. Like red with a stripe down the middle, or green with 2 black stripes etc. etc. but they are not likely to hold their color unless yellow, and even then no guarentees.
Dan