3

I have flat stones which create a patio area in my back yard. In between the stone, the small gaps are filled with pebbles. The stones near the edge of my house are shaded through most of the day and stay damp longer after a rain. As a result they tend to get green algae growth on them.

I have been using chemicals, but as soon as I stop the algae come back, and the chemicals are rather expensive. I was wondering if it would be more cost efficient to buy a UV light that I could plug in and leave shining on the stones for a few hours a day (when its not raining). Would or could this work?

EDIT: I have a pressure washer and have pressure washed it off, but it takes more time then the chemicals, and shoots the pebbles in the cracks all over the place.

dmoody256
  • 131
  • 4

2 Answers2

1

Use of UV for sterilizing water vinegar for killing algae

I am familiar with these UV bulbs and systems for ponds, aquariums and hot tubs. You've got a good idea! But I couldn't find anything about killing algae on surfaces without water.

If you find anyone who tells you that your idea is possible, would you please let us know?

If I were you, I would own a pressure washer. They have smallish easy to use home style for home owners pressure washers. Problem with algae is you wash it off and it will always come back. Chemicals would be tough on your plants as it was washed off. Pressure washing does the same thing without chemistry involved.

Vinegar might be viable to use. Just household vinegar diluted with water? Still not so great for lawns and plants. Just 'spray' from time to time? Allow to dry instead of washing off immediately. You can get an $11 hand pump sprayer (gardening section usually) that would be far easier than anything else AFTER you pressure wash.

Vinegar can make an area of soil unable to support ANY plants or soil organisms. This is a good choice to spray graveled walks, patios, driveways. When sprayed on soil and the cracks, that vinegar LOWERS the pH so low no plant will grow. When you decide to grow plants, one adds lime and brings the pH back up to levels plants and soil organisms can grow.

Better living through chemistry! If one understands chemistry! Grins...I hope this might be a good solution. Could you send a picture of your patio?

stormy
  • 40,664
  • 4
  • 33
  • 76
0

Update

I’ve bumped my original suggestion to the end of this answer as it seems that algae are immune to the effects of ammonium hydroxide.

So, a very cheap solution to your problem is the application of brand-free household bleach.

Household bleach is a dilute solution of sodium hypochlorite.

Sodium hypochlorite is toxic to humans and requires careful application including the use of personal protective equipment such as rubber gloves and eyewear, however I note the following benefits.

  • relatively inexpensive;
  • small amount of concentrate will treat a large area;
  • no detrimental effects to plants.

Continued use over a period of years could lead to a buildup of sodium salts in soil in concentrations greater than what can be synthesised by soil microbiology.

If this presents as a problem, application of gypsum powder may neutralise the sodium salts. Alternatively the addition of fresh compost, peat (or coir-peat = finely ground coconut husk fibre) or activated charcoal or all three will almost certainly balance the soil such that it is productive and nutritious to plants.

Original Answer

A very cheap solution to your problem is the application of brand-free household ammonia.

Household ammonia or ammonium hydroxide is a solution of NH3 in water.

Ammonium hydroxide is toxic to humans and requires careful application including the use of personal protective equipment such as rubber gloves and eyewear, however I note the following benefits.

  • relatively inexpensive;
  • small amount of concentrate will treat a large area;
  • no long term build up of chemical salts in surrounding soil;
  • no detrimental effects to plants.

Always have a Material Safety Data Sheet (or such similar document) on hand when using hazardous products such as ammonium hydroxide, as this document will explain what to do in case of emergency.

andrewbuilder
  • 2,004
  • 8
  • 13