Those my friend are some loaded questions! :)

But I’m happy to answer. In my opinion there are three types of tanks. Freshwater, saltwater with just fish (often called FOWLR - fish only with live rock), and a reef tank (has corals).

My tank is a reef tank. Freshwater and fish only saltwater tanks are cake. Mixing saltwater being the main difference. Corals add probably 2 or three orders of magnitude in challenge, knowledge, required maintenance, and money. Some corals are pretty forgiving and easy to keep, others are downright difficult.

My tank is a small one - 20G. Small tanks are less $, but in my opinion they are extremely hard. Everything about keeping corals is about stability - fish tolerate wide ranges of water parameters, but some corals die overnight if the temp rises a degree, or salinity moves just a bit, etc. Nanos are hard because of the small water volume, one drop of something in my tank moves the needle - one drop in a 200G tank is undetectable. On the plus side, I can “fix” a problem with a large water change (I can mix 20G of water, I can’t mix 400G).

I spend about one half hour per week doing water changes, scrubbing, and doing maintenance. I’ve gotten good at it, when I first started I probably spent 5ish hours a week. It’s worth noting I’ve spent considerable effort building mixing stations and creating a system to do maintenance quickly.

Would I recommend it? Absolutely-as long as you have a few things:

1. You REALLY like saltwater fish and corals - like you don’t get bored of looking at the same fish for coral for 30 years (because that’s how long they live)
2. You are willing to commit to learning a lot first. If you just do it, you’ll fail. I recommend watching the BRS 52 weeks of reefing on YouTube.
3. You have the time and desire to do the maintenance-bigger tanks take more time than mine.

I’ve always wanted a reef tank. I could watch it all day long everyday. Long ago, I realized the $ and commitment required, and backed off because I wasn’t ready. As I got older with more disposable cash, I took the plunge and I’m super happy I did. But it’s been the hardest hobby I’ve ever tried to be successful at and at times it’s been heartbreaking. But I think I’ve figured it all out at this point, and I’d encourage anyone who has the fascination for these animals to take the plunge-it’s worth it if you enjoy these creatures.