The Q&A Archives: Preformed Ponds and Fish

Question: How do I add fish to my preformed pond and what kinds can I get?

Answer: In addition to fish, you'll want plants. Consider a mix of emergent, submergent, and floating species. Emergent plants, those that have their roots in the water but their shoots above water, can be added to the margins of pools. These include cattails (Typha spp.), arrowhead (Sagittaria spp.), and water lilies (Nymphaea spp.). Submergent species, or those that remain under water such as elodea, are often used as oxygenators. These are plants that remove carbon dioxide from the water and add oxygen. These plants are essential in most ponds to keep the water clear. Floating species or those that are not anchored at all in the pond include plants such as duckweed (Lemna minor), water lettuce (Pistia stratiotes), and water hyacinth (Eichhornia crassipes). While attractive, water hyacinth and water lettuce can be serious weed problems in the south; however, since they are not winter hardy, there is no problem with them spreading in northern climates. While not as effective as oxygenators, these plants help keep the water clear by limiting the amount of sunlight that algae receive. In tiny ponds created in barrels and similar containers, these plants may be adequate to maintain clear water.

Choosing and Establishing Plants for Ponds
Consider the following when selecting plants:
How deep is the water? This will be a factor in establishing plants and their survival over winter if you live in colder regions. Some species need a minimum depth of 2 to 3 feet to grow well.
Is your pond permanently installed in the ground or is it a small tub that will be moved inside in the winter? In this case, even tropical plants may be an option.
Will you drain your pond in the winter? If you intend to drain your pond, you should consider plants that can spend the winter in a basement in a dormant state.
How much sunlight does your pond receive?
How large is your pond? If your pond is small, consider dwarf species.
Purchase plants from a reliable vendor. Remember to include some oxygenator plants such as elodea.

Emergent and submergent plants should be planted into pots. A wide assortment of pots is available, from plastic baskets to pulp planters. Choose pots that are large enough for your plants.

If using baskets with numerous perforations, line the basket with burlap or 2 layers of newspaper to keep the soil from falling out of the holes.

Fill the container about half full with a mixture of good garden topsoil. Do not use potting mixes or peat moss. These are too light and will float out of the pot. Adding aquatic plant fertilizer to this bottom layer of soil is recommended for some species. Follow directions on the label for amount.

Place the plant on top of the soil and fill the container with topsoil within one inch of the top.

When planting water lily rhizomes, make a mound of soil in the middle of the pot. Place the rhizome at a 45 degree angle. The crown of the rhizome should be toward the center of the pot. Cover the roots with soil, but not the crown.

In all cases, add a layer of gravel to the top of the pot. This will help keep the soil from floating out and prevent fish from digging in the soil.

Slowly place the pots in the pool to keep soil from floating out. Place pots on bricks to get the desired height.

Floating species can be placed directly into the pond with no other care needed.
Plants should cover 50 to 70 percent of the water surface. Native plants usually do not need fertilizer. For some exotic water lilies, limited fertilizing once yearly may be required. Check with your nursery on care of plants and how deep to place potted plants. Be aware that overfertilizing may cause unwanted algae blooms which can rob the water of oxygen.

Once you've placed the plants, you can add fish. Consider stocking your backyard pond with native fish. They are fun to watch and help keep the pond free of unwanted insects. Most small ponds will warm up quickly in the summer, so make sure you stock with fish that can tolerate elevated temperatures. I've had good luck with what are called "feeder" fish. These are goldfish looking fellas and will grow to substantial size if given room. They are available in any store offering fresh water aquarium fish. You can also invest in Koi for your pond.

You'll also need scavengers, such as aquatic snails and tadpoles, to help control algae.

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