Home » Plants & Animals » Southern Ontario Gardens » Water, water everywhere, and not a sign of algae

Water, water everywhere, and not a sign of algae

© Lorraine Flanigan

I'm just back from Canada Blooms, Ontario's biggest garden and flower show, and now third largest show in the world, and the overwhelming trend is to water gardening. Whether it's a koi pond, rainforest waterfall, or bedpan faucet, water is everywhere, but nowhere did I see a sign of algae.

If you've considered following the water gardening trend, here are a few tips on finding the right balance of water, oxygen and nutrients to support healthy plant and fish life and discourage the growth of algae.

A steady supply of oxygen

Schools of fish and a host of microbes depend on oxygen for survival. Balancing their needs against those of algae can be tricky. You need enough oxygen for fish and microbes to survive, but not so much that algae take over the pond. Planting underwater weeds called oxygenators helps balance oxygen levels in the pond, although the name suggests they add oxygen to the pond, in fact they are important because they compete with algae for excess oxygen and minerals. The goal is to plant enough oxygenators to keep algae at bay.

Another way to ensure lots of oxygen in the pond is to add waterfalls and fountains. Because ponds absorb oxygen at the water's surface, the splash of these features increases the surface area, bringing more water in contact with the air, thereby speeding the exchange of oxygen in the pond.

Nutrients for healthy plants

Finding the right balance of nutrients to support lush plant life yet not so much that algae flourish is another balancing act for pond owners. Slow-release, aquatic plant fertilizer tablets inserted into planting baskets deliver the right amount of nutrients directly to the plants without dispersing them throughout the pond where algae can feed on them.

Some water gardeners also recommend an application of well-rotted manure every three to four years to guarantee an ongoing supply of nutrients. If you decide to use this method, be sure to use only composted manure as fresh manure contains ammonia which is harmful to fish.

Waterworks

It's a fact of life that new ponds develop algae, but fight the urge to change the water or add algicides to control their growth. Although these methods are effective in destroying algae, some can retard the growth of oxygenators which in the long run, play the most important role in keeping algae under control. By changing the water, you introduce an over-abundance of nutrients,thereby encouraging the growth of algae.