ponds, tap water and algae

[pixellent]

I top up my garden pond with tapwater. The disssolved nutrients in the water make algae grow profusely.
Is there any way of neutralising the nutrients or stopping algae growth without using nasty chemicals? I'd like to use rainwater but can never store enough.

[andyjevs]

The dissolved nasties in tap water are not contributing to the algea very much. Fish waste is though !!!! As the bacteria in the pond or filter break down the fish waste, the end product is nitrates and phosphates, which when coupled with sunlight or daylight, produces algeas.

You do not say what type of algea you have.....blanket weed or green water ? Green water is easy to treat by installing an ultraviolet clarifier (UV) but blanket weed is a bit more stubbon and if you don't want to use chemicals, you may have to remove it manually.

But, getting the balance right between plants (oxygenators, marginals and lillies) should keep blanket weed and green water in check by simply starving the algea of its nutrients.

Personally, i'd carry on topping up with the tap water. Rainwater is very acidic and ponds prefer a higher pH of around 7.5 - 8.....rain water would bring it out at around 6.7

Hope this helps a bit

[woofgang]

I top up with tap and only have an algae problem in the first bit of spring, then it all settles down. What I do have is a biological filter at the edge of the pond that takes out the fish waste and breaks it down. The treated water runs back into a bed of irises (planted in a box, tiny pond, only 250 gal!!) which grow like mad and use up the fertiliser in the water. I also have loads of water plants, so many that they constantly need pruning in the growing season!