On hot days, who wouldn't want to hang out near a waterfall! For humans, the water pouring into the pond cools and hydrates the air; for fish, that action acts as a giant aeration system, infusing oxygen into the water beneath the waterfall.
But that raises a valid question: If your fish spend a lot of time near the waterfall, does it mean they're not getting enough oxygen? Yes, it's possible. Here are some questions to ask yourself about your pond's situation.
Is It Getting Full Aeration?
If you're running your waterfall 24 hours a day, your pond is likely getting full aeration. If your pond is more than 24 inches deep, however, and you have a skimmer/waterfall system in place, more aeration may be necessary. Why? Because the oxygenated water will circulate across the water's surface, leaving the water at the bottom of the pond stagnant. Adding an aeration system will prevent stagnation by raising the bottom water to the surface.
Do You Have Too Many Plants?
Plants may release subsurface oxygen to the water during the day, but at night those plants take in oxygen, which means your fish may be gasping for air. If you have quite a few plants and your waterfall is off--and you experience an algae bloom--you should definitely think about adding some aeration.
Do You Have Many Fish?
The more fish in your pond, the more oxygen you'll need--which means you'll need more aeration and possible additional filtration to help keep the water clean. Unless you have a filter large enough to handle the fish load we recommend keeping one 6- to 8-inch fish per 10 square feet of surface area.
How's Your Muck Level?
Another clue that your pond had insufficient oxygen is the amount of muck that has accumulated at the bottom of your pond. When your pond is properly aerated, muck naturally breaks up thanks to the growing population of aerobic beneficial bacteria. If there is not enough oxygen present, debris will accumulate at an faster rate.
What Temperature is the Pond Water
Cooler water holds more oxygen than warm water, if your pond is in full sun and water temperatures are reaching the high 70's to 80's there's a good chance your fish are struggling to get the oxygen they need. A partial water change may help relieve the immediate issue but adding surface floating plants, providing other sources of shade and double checking that you have enough circulation will help to ensure it does not remain and continuing issue.
Did You Recently Treat Your Pond?
You must be careful when treating your pond, especially pea green water or planktonic algae during hot summer months. Most algaecides work very quickly. When the algae die, they begin to decompose immediately, robbing oxygen from your fish. If you suspect this is the case a partial water change, 10-20%, may help relieve the stress and get your fish some much needed oxygen quickly.
If any of these scenarios apply to your pond, we recommend adding the energy-efficient aeration system. They help to circulate the water and add valuable oxygen, providing the best possible environment for your fish.