photo by Anita Warren Hampson

Fishy business

If you’ve ever considered a fishpond but thought your yard wasn’t right for it, Kristi Smith, of Longmont-based Colorado Pond Pros, begs to differ.

By Lisa Truesdale

Almost any yard can fit a pond, she says, as long as the pond is set up correctly. Here are Smith’s tips for raising fish in a backyard pond.

  1. Choose aquatic plants that will shade the water. “If the water gets overheated, it promotes algae growth. Also, the fish need cover to hide from predators and shade to avoid getting sunburned.” You’ll want a mix of floating, deep water and marginal plants. Some choices are water hyacinth, water lettuce and water iris. Invasive plants, like cattails, should be kept in pots or baskets. Koi can be aggressive and destroy plants, so check with a pro to determine the best plants and placements for your pond.
  2. Know your species. “Many people who think they have koi actually have goldfish,” Smith says. Koi are slimmer than goldfish, with barbels (like whiskers) and beautiful fins. Goldfish are plumper and usually smaller.
  3. Determine how many fish your pond can accommodate. Too many fish can create an imbalance in your pond’s ecosystem and ultimately harm the fish. Since goldfish are smaller, a pond can usually have more goldfish than koi per cubic foot of water. A pond designer (or online pond-stocking calculators) can help you determine how many fish you should get.
  4. Protect your fish. Plants will help them hide from predators, but a fish cave also gives them a place to overwinter. Consider netting or a sprinkler that automatically engages when movement around the pond is detected, and set up plastic decoys like blue herons that scare off birds. Also, make sure the pond has steep sides and walls to make it harder for raccoons and other predators to access it.
  5. Don’t overfeed your fish. Since fish also eat algae in the pond, they don’t need daily feeding. Smith recommends weekly feeding (the amount will depend on how many fish you have). Overfeeding dirties a pond, as uneaten food sinks and decays.
  6. Choose the right depth for your fish. Check with a pond professional to determine the right depth for your pond; 2 feet is the shallowest depth that works for goldfish; most koi need a pond that is at least 3 to 5 feet in depth. Avoid a shallow depth that will freeze solid and kill the fish.
  7. Don’t worry about fish in winter, as long as your pond is deep enough. “Fish overwinter just fine in Colorado,” Smith says. “That’s because their systems slow down, they don’t eat and they don’t move much.” When the water temperature reaches 50 degrees, they become active again.
  8. Keep your pond free of decay. This is especially important in fall, when leaves may litter the pond. Skim off plant materials before they have a chance to decay, and consider adding beneficial microbes to help keep the pond clean.
  9. If you ever find that you have too many fish, don’t release them in a natural pond or lake. “They’ll likely die in that environment and mess up the established ecosystem,” Smith says. “Call a pond designer; we can help with rehoming.”

Illustration by Grey Lilac

A healthy fishpond relies on five elements, Smith says:

1- Mechanical filtration to keep out debris.

2- Rocks and gravel for biological filtration. Don’t use flagstone, Smith cautions, as it could break down, leading to excessive algae and setting the pond up for failure.

3- Recirculation and aeration to keep the water oxygenated.

4- Aquatic plants for living filtration and shade.

5- Fish, which eat the algae and help keep the pond clean.