Put the plug into the sink then use sealant; the same type that’s used around the edges of a shower or bath. Squeeze the sealant around the edge of the plug and plug hole so it forms a tight waterproof seal and water won’t escape from your sink fish tank.
Find a suitable place in your garden or patio area. A place where you can easily see the sink fish tank and enjoy the fish is best.
Place the sink next to where you intend to set up the sink fish tank. Dig a hole in the ground using a shovel. Make it slightly larger than the sink, but try to get the contours correct so it can sit level in the hole.
Put the sink into the hole then shovel some of the dirt that you dug out to make the hole back into places where there are gaps between the sink and the outer edge of the hole. Pack the dirt in tightly, so it holds the sink firm. As you do this, use a level to ensure the sink is level. Make the sink level by gently tapping raised areas using a wooden mallet.
Find rocks or large stones from around your garden. Try to find ones that are reasonably attractive. Place the rocks or stones around the edge of the sink so it covers up the sink edges. This makes sink fish tank look natural to the environment.
Put some plants, suited to growing with little soil requirement, among the rocks and stones. This will turn your sink fish tank into an attractive water feature.
Fill up the sink fish tank with water. Let it stand for a couple of days to settle, then buy some suitably sized fish to stock your tank.