PUZZLE 078 A Cold Fish

There is a sunny island that's always warm.
A popular fish sold at the shops is packed in ice to keep it at the optimum temperature for freshness.
It needs two blocks for one day, and three blocks for two days.
So, for example, five blocks would be required for three days.
A new fish has just been caught.
What is the minimum number of ice blocks needed to keep it fresh for one week?

Hint 1

Picture the scenario of trying to preserve the fish, and figure out a way to reduce the number of ice blocks required.

Hint 2

To keep it fresh for one week, or seven days, you would need blocks for 2 days + 2 days + 2 days + 1 day, making a total of eleven blocks.
But there's a way to keep it fresh that would require less blocks.

Hint 3

The fish you need to keep fresh for a week has only just been caught, and is still very livery.

Super Hint

If you put the fish in a tank and let it live, you wouldn't need any ice blocks.
So how many ice blocks do you need?

Answer for 'A Cold Fish'

The answer is '0'.