Here's a pic of the 110g indoor goldfish pond we built years ago when we decided to keep three goldfish:
Here are what the fish looked like while playing in the water flow:
Man, I just loved watching them swim in that large space, especially when they swam in and out of the water flow
Only had them about three years, so they were still pretty small. I wonder if we had kept them when we moved if we would have built them larger digs.
Here's our goldfish webpage:
http://www.lostmymarblz.com/indoorpond.htm
Sorry to hijack the thread, though....
Here is the page of our 2.5g reef:
http://www.lostmymarblz.com/2-5galreef.htm