With saltwater (I cannot begin to speak intelligently regarding freshwater fish as my experience is limited to my sons beta), they are extremely sensitive to water pentameters for the most part. When you read about a saltwater fish and it says that it is "easy" to maintain, that means that it can handle a little less than perfect water however most need a good stable environment. I did read the threads posted however I can't judge simply because I've killed ever goldfish I've ever owned.
There are a few things you have to know about saltwater tanks. First off, smaller tank DOES NOT mean easier but difficult! The smaller the tank the more cleaning and maintenance you will have even with a great filtration system. The next expectation should be cost in my opinion. Once you've decided to take on the challenge of salt, you need to know that there are things you cannot live without if you want to be successful. IMO
, you will need a test kit that tests for ammonia, nitrites,nitrates, phosphates, Ph. That's for fish only with some live rock. In a smaller tank, using reverse osmosis water is imperative because of the ability of waste to quickly build up. Dilution is the solution...more space and water equals less toxicity over a period of time. That's one reason in saltwater everyone says to go as big as you can afford. Using tap water or well water generally contains phosphates to start with and that's a major cause of algae issues. Since you are going with a fish only tank, and since it's small you wouldn't need a canister on something like that. I'm unfamiliar with what it came with as I've always bought my tank and all the things for it separately. I'm guessing it may need to be upgraded. You should always use a system that can handle more than you have. You should only plan on two small fish in the aquarium MAX. I know that freshwater lets you put 1 fish per gallon however saltwater is much more dense. Adding lots of fish will equal killing lots of fish. Since you live in Alaska, make sure you have a heater. You should have a power head I would think. I've had a little 20 gallon tank and it was fine however you can't put off water changes etc. Keep meds on hand for ich and common diseases or parasites that your specific fish are most susceptible to. At one point you will need them sooner or later. Never dose the tank, put them in another tank or container to do this. Once you dose your tank with copper you pretty much will kill any snails or crabs and it's now contaminated so it's likely any replacements will die. You need to research what fish you want, size they will reach, foods they eat, and any special needs they might have prior to buying them. If a fish has a 50 gallon requirement that's the minimum amount of space it will need as an adult to live in without stress.
I have a list of stuff and this is already long. I don't want to question your commitment. I am only wanting to inform you so that you have the right expectations. Having saltwater fish is fun but challenging!