Not sure what you mean by a "saltwater" tank. Pretty much any tank can be used for SW
. The only caveats would be one of those ancient metal framed tanks, or a tank that was used for FW
and dosed with copper containing meds.
You can start with a FOWLR
tank and then get some corals later. That's what I did. Live rock on its own doesn't need special lighting but you can have that lighting if you want. I have a friend with a 29 gallon reef tank with 2x65 watt CFs and he has several happy soft corals in there.
Most salties don't actually use a filter, at least in the freshwater sense. The biological filtration in a FOWLR
or reef tank is provided by the live rock. A skimmer helps to remove excess organic stuff dissolved in the water, powerheads provide circulation, and a "clean up crew" of snails, hermits and other inverts takes care of most of the detritus. Filter media produces a lot of nitrate which is OK for fish but bad for corals, which is why most reef tanks don't have filters. The only instance that I can think of in a SW
setup where you'd want a filter would be a fish-only tank with big, messy eaters like triggers or puffers.
As for fish in a 29g, you're a little limited, but 2-3 small fish would be fine. Damsels are cute and hardy but can be ferocious little beasties. Gobies, blennies, firefish, pygmy angels, clownfish and grammas would be good fish to research. I had 3 fish in my 30 and they were happy but that was definitely enough.
So the basic equipment would be:
-Tank (as big as you can afford)
-lights (what kind depends on what you want to do)
-salt mix and a refractometer
-base rock and some live rock (base rock is cheaper and will soon become "live")
-substrate (aragonite sand is what most people prefer)
-the usual odds and ends (thermo, nets etc that you probably have), saltwater test kits
Determining which of each of these to get is the hard/fun part, and you'll get plenty of advice on here about that. First thing to decide is what size tank you want, as everything else is kind of based on that.