I used to sing this in folk clubs that would let me. It then went:

The Goldfish is a solemn bloke
He just swims round and round
And round and round and round
And round and round and round

He lurks beneath the water but
He never makes a sound
And round and round and round
And round and round and round

He opens up his mouth to speak
But you'll never hear a sound
He just keeps swimminground and round
And round and round and round

Sometimes he swims towards the sky
Sometimes towards the ground
But generally he just swims round
And round and round and round

And when it's time for him to eat
I'll bet an even pound
He'll keep on swimming round and round
And round and round and round

And when the mating season comes
He doesn't leap or bound
He'll just keep swimming round and round
And round and round and round

And round and round and round
And round and round and round
And round and round and round
And round and round and round