Humid weather is spiking pool algae

Humid summer weather is playing havoc with Hamilton swimming pools. Pool owners are being urged to stay vigilant with water treatments and maintenance as the weather causes a spike in mustard algae.

The mustard algae looks like sand on the bottom of pools, and clouds up in the pool water if brushed or attempts are made to get rid of it.

Hamilton East's Le Vonne Paul said the algae suddenly appeared several weeks ago in the 11-metre concrete pool at her rental home. "We were on to it – we have a pool valet, yet couldn't get rid of it."

Her pool water alternated between green and blue for several days. Ms Paul said she upped the number of chlorine tablets going into the pool water, eventually using a high-dose "chlorine shock treatment" to kill the algae.

Ms Paul, who is managing a pool for the first time, said dealing with the problem had been "hugely expensive" on top of the already costly pool maintenance. "We've just about used our three months' supply of chlorine in one month."

She said the algae was frustrating as it was ruining the experience of using the pool, creating extra work maintaining it, and the tiny organisms were not being removed by the brand new filter fitted to the pool. Togs and equipment had to be thoroughly cleaned.

Hamilton's Swimming Pool Shop manager Cheryl Park said several of her customers had commented on the emergence of the algae in their pools, and it was believed to have been caused by weather conditions.

"We've had high humidity, we've had thunderstorms and, yes, it plays havoc with the pools," she said.

Customers reported algae being harder to get rid of than previously, although algae could differ from pool to pool, and her company could not test for different strains. She urged regular checks on chlorine levels and pool owners should make sure they filter long enough.

K Drive Pool and Spa Ltd's Diane Anderson agreed. She said her customers had also been complaining this summer about increased algae, which has been clinging to the sides or bottom of their pool.

Ms Anderson said concrete pools were more susceptible to the algae.

She said it was important that people with pools had their ph (acidity) levels between 7 and 7.4.

Mike Alexander, general manager of Auckland firm Waterco – the firm which supplied Ms Paul's filter – said the algae had been around for some time, and mustard algae was not uncommon. "If it's mustard algae, it will balloon up in the water," he said. "It's very fine, so the filter doesn't catch it."

His firm used an algae killer, and the algae would then settle on the bottom of the pool. Mr Alexander said it was then crucial that pool owners "vacuum to waste", rather than returning the water to the pool through the filter.

"If any [algae] is left, and not killed, it multiplies very quickly," he said. "With warmer weather, all algae multiplies – and your chlorine gets burnt off very quickly." There was no need to remove all the water from the pool, he said.

- © Fairfax NZ News