so you want a SW ray. 
the california stingray, u. halleri
or cortez stingray, u. maculatus
and bluespotted stingray, d. kuhlii
are some nice "starter" species.
but i have a feeling 500-600 dollars isnt going to be enough for the system that these fish need. craiglist will be a great help to you, but often the tanks for sale are meant to be used for freshwater. with slightly heavier saltwater, and a large tank, well, you want some thicker glass.
with rays that need some serious surface area, alternative tanks like stock tubs, plastic pools or fibreglass tanks have been used with great success. [you don't really need side-viewing with elasombranchs, rays especially. it really can cut costs]
doing-it-yourself [there're lots of plywood tanks and ponds around the forum] would cut costs quite a bit too but you'll have to decide whether you're equipped for that.
for your life-support system, think a big skimmer, lots of live rock in a big sump or sumps, biotower, a refugium. sand filters are sposed to be great for big SW systems as well, but i dont know much about them personally.
we've got some great elasmobranch keepers around here, can't wait to see what they advise.

the california stingray, u. halleri
or cortez stingray, u. maculatus
and bluespotted stingray, d. kuhlii
are some nice "starter" species.
but i have a feeling 500-600 dollars isnt going to be enough for the system that these fish need. craiglist will be a great help to you, but often the tanks for sale are meant to be used for freshwater. with slightly heavier saltwater, and a large tank, well, you want some thicker glass.
with rays that need some serious surface area, alternative tanks like stock tubs, plastic pools or fibreglass tanks have been used with great success. [you don't really need side-viewing with elasombranchs, rays especially. it really can cut costs]
doing-it-yourself [there're lots of plywood tanks and ponds around the forum] would cut costs quite a bit too but you'll have to decide whether you're equipped for that.
for your life-support system, think a big skimmer, lots of live rock in a big sump or sumps, biotower
we've got some great elasmobranch keepers around here, can't wait to see what they advise.
