Fish in a 20

[ReeferBill]

Start off with the 20 gallon long for a beginner tank and if you can keep a few fish and grow some softies and LPS then graduate to a larger set-up like a 75 gallon and turn the 20 into a refugium or sump.

 

[Bunnylicked]

You could always turn it into a goby tank and get a few pairs of tiny gobies.

If you get SPS, try starting with some montipora and birdsnest corals. Mine are growing like crazy in my pico, and I've only been keeping reefs since August.

 

[Kiviro]

Like I said, I'm well prepared for SPS corals.