After years of work, Taipei's Danshui River is finally becoming cleaner. Recently, the EPA found that the monk goby fish which had gone missing for many years had reappeared.

The existence of this fish, means the river has a a milder level of pollution, but it will take another two decades for the river to be truly clean.

The sun shows that the Danshui River oxygen levels are too low, resulting in a large number of dead mullet.

However, the condition of this river has improved to that of moderately polluted.

The EPA also found recently the monk goby fish that 20 years ago disappeared from the river.

Scholars say that indeed this is representative of a relatively clean estuary.

The EPA says that a clean river mouth is necessary as these fish swim into the upper reaches of the river to lay their eggs.

This indicates a lower level of contamination, but if one wants to return to a period when the river was the most clean to see sweet fish return, it may take 20 years.

The hugely expensive restoration of the Danshui River is slowly gaining momentum as the EPA says that compared with an investigation in 2002, the number of species have tripled.

However, dissolved oxygen levels still need to rise higher for more fish to come back.