Carassius auratus:, Gold Fish The Latin here is quite generic as there are at least 4 types in this pic alone.http://en.wikipedia.org/wiki/Goldfish
These guys are about two years old. all around 10 to 15 cm long. There are Koi as well but none in this pic. Gold Fish are easy to have in a pond but be careful. The biggest single mistake we all make and I included is to over stock your pond with them. This leads to much grief for the fish and for your self. The more fish in the pond the greater the up keep. My rule of thumb is about one to every 400 liters of water or 100 USA gallon. Fish in nature do not usually live a crowded life. These guys do tolerate a lot where other fish will not. Still to keep them healthy that is a great way to go with little cost.
Big thing for these guys is to give them lots of protection. The reason that these are all two years old is that my neighbour feeds the seagulls and when they spotted the fish they had an extra treat on the side. In a few short minutes they where all gone. Lots of side cover plants floating plants and places for them to hide under water are ideal. Also avoid ledges and slops in your pond as this helps the raccoons. My pond is less than 1 meter deep and it works for me. however it really should be deeper.
Remember kids love ponds and there are kid hazards involved with any water feature