Steamed cod in garlic black bean sauce

I bought a bottle of garlic black bean sauce thinking how convenient it is to just put the sauce as it is without adding other seasoning. But it did not taste like how I would like it to be (just tasted very salty.. >_<) and so the bottle of garlic black bean sauce was quietly put aside in my fridge until I saw it again during my recent fridge clean-up. Decided to try and use the sauce again and this time it tasted so much better.

Ingredient
Cod fish (or other white fish)
Ginger slices
Chopped spring onions
Chopped garlic
Cornstarch solution 

Marinate
White pepper
Soy sauce
Chinese cooking wine

Sauce
1 tsp garlic black bean sauce
1 tsp oyster sauce
1 tsp soy sauce
Some water (approx half a small bowl)
Sugar (approx 1/2 tsp)

Recipe
1. Marinate the fish with the seasonings stated in marinate and let it sit for 5 minutes.
2. Put ginger slices on the fish and steam it together with the marinate until cooked. Mine took about 12 minutes on electrical steamer.
3. While steaming the fish, fry some garlic in the saucepan until fragrant. Add in the seasonings stated in sauce except sugar. Let it come to a boil and add sugar to adjust the taste.
4. Thicken the sauce with cornstarch solution. You may skip if you prefer it to be watery consistency.
5. Remove the steamed fish and place it on a deep serving dish. Pour away the steaming liquid. Now pour the sauce over the fish and garnish with chopped spring onions.