Hi! (I'm going to precede this by saying I've only been researching saltwater for about two months and have only just bought a tank which hasn't even been filled yet, so take all this with a grain of salt. I would highly recommend joining a saltwater forum like reef2reef due to the sheer amount of knowledge they have there, however there are also saltwater experts somewhere on here too
).
From what I've seen, saltwater is generally considered more complicated and definitely more expensive than freshwater- however, it also depends on how complicated you make it. For example, if you set up a tank with expensive and hard to keep corals, that is going to be radically more difficult, time consuming, and expensive than a FOWLR system (fish only with live rock- basically a tank with only fish and no corals).
Good news- clownfish are one of THE best beginner fish, being hardy and able to be kept in (relatively) small tanks compared to other saltwater fish. Clownfish are generally best kept in pairs due to several reasons- juvenile clownfish are all male (or gender neutral), and when bought in pairs at a young age, one will make the transition to becoming a female (you can tell which is which because the new female will be bigger than the male and there might be some bullying behaviour at the start from the female to make the male submit). To avoid any potential issues, you can just buy them in already-made pairs (one bonded male and female), but I believe this is usually more expensive. The best clownfish to keep in smaller tanks is generally
ocellaris (the 'nemo' looking orange and white ones, but they come in several 'designer' colours including black and white).
For other fish, I don't know very much about saltwater nano-fish, but a yellow-watchman goby and a pistol shrimp is a popular option for small tanks and come with a very cool symbiotic relationship (the goby stands watch against predators for the shrimp, which is pretty much blind and digs a home for them to live in. The shrimps also make clicking noises with their claws).
Clownfish don't
need anemones in tanks (they live in other corals or even just choose a piece of rock they like), and honestly I wouldn't recommend anemone for a beginner (I'm not thinking about getting one
ever, they seem like royal pains). Anemones need very stable, established tanks (6 months+), and are prone to moving around depending on whether they like the conditions or not. They also split themselves to reproduce, so if they like your aquarium you go from one anemone to six in a relatively short period of time. Furthermore, if they die (usually from being sucked into a filter or powerhead), they have a tendency to 'nuke the tank' (they release a very high amount of ammonia into the water and kill fish, corals, and invertebrates). The best 'beginner' anemone if you really want one is a bubbletip, which come in several colours and clowns can symbiotically connect to.
As for tank size, the recommended tank size for fish is a very controversial topic- long term a 20-gallon tank is usually considered the best if you want another fish, but I got a Fluval EVO 13.5g (I like this option because it already comes with a filter and decent light, which saves costs), and I'll only have a pair of clownfish. This is
generally considered ok, but I wouldn't go any smaller than that. As far as I know, taller tanks aren't as good as longer tanks for pretty much every fish.
Sorry for the long reply, if you can't be bothered to read any of that, my main message is basically- do your own research, and maybe wait out on saltwater for a while if you're not super confident with freshwater, because it is more complicated. Sorry if I freaked you out.
PPJ
