You can buy vegetable, beef, and chicken stock, but I rarely see fish stock in the supermarket. Instead of buying stock cubes, which are often too-salty in my opinion, why not make your own? Here's a quick fish stock, which makes use of an otherwise waste product.
Cooking Time: 30 minutes
Makes: Half a mug
Ingredients Excess fish bones (ideally a whole fish)
Once you have removed all the meat (as best you can), from the bones of the fish you have cooked you should be left with a few flakes of fillet still clinging to the bones, perhaps a few scales, and if you're lucky, a fish head.
Place the bones in a saucepan of boiling water.
Simmer for 30 minutes and cover with a lid.
Pour the stock through a sieve into a bowl and discard the bones.
Pour into a mug.
Keep the stock in a cup/mug and store in the fridge/freezer for future use.
The flavour from fish bones is incredible - you'll never buy stock again.