I've maintained everything from 0.5 gallon to 4 gallon tanks, the painful part was actually the weekly water changes, although it was easy enough to dispense seawater for 15 minutes and change the water for 15 minutes, but it was still tougher for me to keep it up for 3 years. Looking back, I have kept quite a few corals, so I know what corals are best for me to keep or what I like best. The reason why small tanks are hard to keep is actually persistence, sticking to a fixed time for water changes, trust me, change for 3 years and you will understand what pain is. So I stopped keeping it for a while and felt a sense of relief that I didn't have to worry about how the tank would be maintained in my long absence. Now I've started keeping it again because I picked up a small anemone on the beach, and yes, for the same reason I started keeping it back then. Since I picked it up on the beach, I tried to turn my tank into a seaweed tank and keep the anemone alive and happy. The good thing about a seaweed tank is that you don't have to change the water very often as I don't intend to keep a lot of corals. A small tank and a big tank look different, but really they are both just a ladle of water compared to the ocean. So looking at the tank correctly, putting the right amount of live rock, sand and corals to keep them happy is the most important thing, giving them enough space to stretch out rather than crammed together like a vase, of course I admit the right mix would look great, but personally I am happy to keep my seawater tank like an aquarium at the moment, even to see the little bugs crawling back and forth on the rocks, because I want to keep it longer and more relaxed. I really don't need a lot of corals, just a few of my favourites, but how many people can control their own fancy?