Double see-thru = viewing from both sides. I have a client now that has a perfect spot in their basement for a tank(s) but they dont want the work that would come with fish.
the fish looks happy in the pipe. about time for a new pipe. lol Show a picture of your fish like that to a plumber and I bet he would give you a piece for a new home.(soften the edges with some sandpaper before giving it to him)
well if you got some wood skills I would try to trim it out in a hardwood. I can see the whole build in my head. if you lived closer I'd come over and give ya a hand.
I could tell ya how to build it but you would have to give me a little while to get some drawings made up.