Freshwater for a beginner.
Sure, maybe the marine/salt water fish are prettier and more interesting to look at, but I just didn't want to throw money at a hobby that I wasn't sure I knew what I was doing. It wouldn't be fair to me, nor the delicate fish.
I chose the freshwater of salt due to my in-experience. After discussing salt water with my friends, it seemed to me a lot more maintenance and finances would be initially outlayed....and the results in my case would most likely not be good.
So then, it was deciding wether it be cold water or warm. I really black Black Moors, but I was amazed at the level of growth that fancy goldfish may aqcuire, and I wanted a little bit more control and variety in my tank. I also wanted a subtle challenge in water chemistry and it seemed that cold water may be a bit too easy for my interest level. So warm water it is.
Then the tank size: Yeah, I'd love to get a 40
gal, maybe even a 29
gal, but as a complete novice (and discussions with my wife) it ended up being a 16
gal bow-glass. I understand that water stabilization may be better at 29+
gal's, but size limitations in my condo and fear of really borking anything up made my decision for me. Also, we plan on moving perhaps in a year or two, and I'd like to think I had the foresight that a 16
gal aquarium would be easier to move than a 30+. When we get a real house someday and know we are going to be there a while, then a bigger tank will be in my future.