If there are no fish in my fish tank, is it still a "fish" tank?

Shark week on the Discovery channel is about to end. I hope the last shark program goes out with a bang. Some of the programs I have seen talked about great white sharks (ホオジロザメ). They are very mysterious and beautiful. I just hope I never see one while swimming in the sea.

Speaking of fish, a few weeks ago, we bought a fish tank. After seeing Finding Nemo one time too many, we couldn't resist not buying some clownfish (カクレクマノミ). However because of my inexperience with fish keeping, the fish kicked the bucket. When it comes to salt water fish keeping, I feel like a fish out of water but I hope to get the hang of it.

Here are some more "fish" expressions and idioms. Can you think of any other ones?

idiom-- have bigger fish to fry/ have other fish to fry
meaning-- to have other things to do; to have more important things to do.
sample sentence-- I won't waste time on your question. I have bigger fish to fry.
From the ALC site-- have bigger fish to fry

ほかにもっと大切［大事｛だいじ｝］な仕事｛しごと｝がある

idiom-- There are plenty of other fish in the sea.
meaning-- There are other choices (to talk about people)
sample sentence-- When Takeshi broke up with Keiko, I told her not to worry. There are plenty of other fish in the sea.
From ALC Space--Why do you think he is the only nice-looking man in the world? Look around, there are plenty of other fish in the sea.
この世で格好いい人は彼だけじゃない。周りを見てごらんよ。格好いい人は他にもいる。

idiom-- go out with a bang
meaning-- finish successfully, finish in an exciting way.
sample sentence-- The Sopranos finale went out with a bang.
From the ALC space site-- Tim won't retire quietly. I assure you he will go out with a bang.

ティムはひっそりとは退職しないでしょう。きっと、賑々しく辞めていくと思います