I like this thread, because it's full of stuff I would like to have known when I started. Those of us who have enjoyed this hobby for a long time can develop an overview of what does and doesn't work.
I think we start by seeing fish as commodities, and hopefully we quickly realize they are living creatures with natural histories that go back to long before aquarium stores existed. When I had hard water, I thought I was really good keeping softwater tetras for 3-4 years. Now, with soft tapwater, if they don't make 7 I'm trying to see what's wrong. It's never one size fits all in nature, but soooo many hobbyists believe all fish adapt to all water. There's a myth that they adapt to radically different conditions than they spent tens of thousands of years in over the few years they've been farm bred. It's truer that we've accepted them living shorter lives because it's convenient to think that way.
A glowlight tetra comes from slightly harder water than a cardinal, and lives very differently than a piranha. Forget the all tetras are the same to keep bs. They aren't divided into species for nothing, and each one has to be learned and well treated for what it is.
It's like plants, too. I have a stone thumb. I know my limits. I research plants and only buy the easy ones. A lot of stores sell hard to get started cuttings, or land plants that survive temporary flooding (and so, die soon in tanks). The best work around is to take a look before you go to the store, make a list of what you think you can handle, and then go hunting.
I always try to look up where in the world a fish comes from. Then I check a map. Coastal? Chances are it'll like harder water, so if I have that from the tap, I look up more on the fish.
In time, you'll learn to adjust water to the fish. It's easy if you start with softwater, and really difficult and more expensive if you start with hard. But forget that when you're starting - pick fish that will thrive in what's easiest for you.
There are plenty of great species to get in your tank, Galaxy Rasbora, Emerald Rasbora, Rummy Nose Rasbora, small Synodontis species like Lucipinis and Polli and smaller Rainbowfish like Dwarf Neons, Kamaka and some of the Forktail species, Amano Shrimp do great and so do some of the fancy snail species like Rabbits and Cappuccino. Livebearers like Swordtails, Platies, Guppies would all do great as would some of the rarer species like Limia and Skiffia. Some of the smallest Central American Cichlids like Nanoluteus or Cutteri would work in here too but you'd need to go with the bigger of the species I mentioned. Again with the bigger species Golden Wonder Killi would be a good option too.
