Ellen,

The first thing about keeping anything in a salt water tank is to get a
book, or better yet a couple of them.  Of course, reading them is also not
too bad an idea.  Salt water setups are not difficult, but they are a bit
more demanding than fresh water - for a number of reasons that any decent
book will explain.  The size of the tank ought to be as large as you can
afford or have room for.  The larger the tank the easier it is to maintain
stable water conditions.  And this is the trick with salt water.  The oceans
(even though very different from place to place) are extremely stable when
compared to any fresh water environment.  Maintaining water quality and
stability is the real trick to keeping salt water fish or invertebrates.

When you read up on the subject you will find a number of systems with
different lights, filters, salt mixes, substrate, etc.  All pretty much
work, just decide on one that looks reasonable and press on.  I started in
salt water in the 1950s when almost nothing was known about how to do so
with any success.  Since then the hobby has matured a lot.  At present I do
not have a set up, but I do have a 75 gallon tank in the garage ready to go
when I finally decide to get back in to it.

Xenos are detritus and algae grazers as far as I know, so should be fairly
easy to maintain.

Again, hit a pet store or library or bookstore and get those books.  They
are the very best way to start.

Good luck,

Tom Eichhorst in New Mexico, USA