A man has been fined after his backyard pool fell into such a state of disrepair it resembled a swamp and became a dangerous breeding ground for mosquitoes, creating a health hazard in the neighbourhood in Perth's north.

Joondalup City Council went to court and secured a fine against the man over his pool in Currambine, which was described as having "black" water.

The city alleged that David Noel Fuller "did not keep premises free of water that was liable to become the breeding place of mosquitoes".

Fuller was fined $2,700 in the Joondalup Magistrates Court, in addition to costs of $933.35.

He had already been fined in 2017 for failing to fence the pool — the impost on that occasion being $1,500, with costs of $933.

In a statement issued to the ABC, Joondalup Council chief executive Garry Hunt said the city took the prevention of mosquito breeding very seriously.

"Mosquitoes are known carriers of infectious diseases, such as Ross River virus and Barmah Forest virus, and poorly maintained pools allow the potential for breeding to occur," he said.

"The city investigated the condition of this resident's pool and the potential of mosquito breeding independent to the investigation on the pool's security."

He said the city would continue to work towards a resolution with Fuller.

The pool had degraded to such a level its "black" water resembled something that came from a swamp. ( ABC Open contributor rene52 )

An uncommon case

The WA Health Department's managing scientist of environmental health hazards, Michael Lindsay, said such prosecutions were uncommon.

"It's a risk-based approach and the first thing that has to be done is to show that the type of mosquito that's breeding there is a potential carrier of a virus, like Ross River virus," he said.

"There are some mosquitoes that will breed in domestic settings like that, such as swimming pools or other artificial breeding sites in our backyards, that may not be a disease risk but which can cause a substantial impact on amenity for neighbours — and in fact for the residents of the house as well — even though they might not know that it's coming from their own backyard."

Dr Lindsay said there were more than 100 different types of mosquitoes in WA.

"They've managed to successfully colonise just about every still body of water that you like to think of, whether it's a salt marsh pool, or whether it's a big billabong up in the Kimberley, or it's containers, or swimming pools in people's backyards," he said.

"It's really undesirable to create high levels of breeding across our urban environments."