How to Make a Mini Outdoor Pond for Aquarium Fish

When the weather warms up and summer is upon us, everyone is itching to go outside. What better way to enjoy nature than to set up your first mini pond for breeding aquarium fish? If you live in a temperate climate that experiences distinct seasonal changes, then your mini pond fun usually lasts for 3 to 4 months in the summer (e.g., sometime between May and September in the United States). However, if you live in the subtropical zone that stays above 50°F or 10°C for most of the year (like Florida), then you can play with fish outdoors all year round.

Nature does a spectacular job of raising fish in many ways, and we can learn some valuable lessons by putting our fish outside. Fish and shrimp develop brilliant coloration when grown under sunlight and fed natural foods like green water, algae, fallen leaves, and live insects. Mini ponds not only house an abundance of fish babies and plants for you to enjoy, but they also attract all sorts of wildlife – such as bugs, frogs, birds, and even deer. In times of drought, your pond may become a vital part of the local ecosystem.

How Do You Make a Mini Pond?

Finding a container is one of the easiest parts of making a mini pond. You can start with something as ordinary as a 5-gallon bucket or purchase a giant 300-gallon plastic stock tub from a livestock feed store. Other ideas include old aquariums, kiddie pools, and half whiskey barrels. In general, larger containers are preferred to help minimize water quality issues and temperature swings. Also, containers made out of metal may not be conducive for keeping shrimp and snails, since invertebrates are more sensitive to trace metals in the water.

Even large, decorative pots can become beautiful mini ponds for your backyard or apartment balcony.

The location of your container can play a significant role in temperature management. For example, place the container under shade if at all possible. The temperature won’t change as drastically, and less algae will grow. (Algae is good for your fish, but it may not be as desirable if you plan on growing plants for profit.) If nothing casts a shadow large enough for your container, consider using a shade cloth to decrease the sun exposure. Another tactic is to bury the container partially or entirely in the ground since the earth will help the mini pond stay cooler in the summer and warmer in the winter. However, they also require extra precautions like safety fences to keep out small children and pets (just as you would do for an inground swimming pool).

When it comes to filtration, a simple sponge filter with an air pump should suffice for a mini pond, but you can also buy a pond filter or make your own DIY bucket filter for keeping larger fish like goldfish and African cichlids. An important step is to protect the electrical equipment from sun and rain. One method is to shelter the air pump inside a garage and run airline tubing outside to the mini tub. If this is not possible, get a weatherproof connection box from the hardware store to protect any power cords and extension cables. You’ll also need to cover the air pump itself inside a weatherproof box or underneath an upside-down tote to decrease UV damage.

Once the equipment is set up, fill the container and add dechlorinater to make the tap water safe for fish. Rain should help replace evaporation from the mini pond, but you may need to top it off with the hose if there happens to be in drought. In the rest of the article, we'll talk about plants, fish, and predator deterrents to add to the mini pond.

What Are the Best Plants for a Small Pond?

We highly recommend adding aquatic plants into your pond because of the many benefits they provide. Plants offer shade and shelter for fish to hide from predators, as well as landing spots for insects and amphibians to take a drink. Water hyacinth is a very popular pond plant because of its beautiful purple blooms and long, bushy roots that provide valuable cover for fry. They’re commonly used by water treatment plants because of their incredible ability to pull out organic waste and toxins from the water.

Water hyacinth in bloom

Other plants for your pond include duckweed, water lettuce, water lilies, lotuses, and even aquarium plants. Toss in some water sprite or other stem plant trimmings, and they will flourish and multiply under the natural sunlight. Because of the power of plants, there’s no need to worry about any fallen leaves, branches, or other decaying matter in the container. The plants purify the water, and your mini ecosystem (consisting of algae, microorganisms, and fish) helps break them down. 

What Fish Can You Put in a Small Pond?

This question requires some additional research on your part in terms of how long certain fish can stay outside in your climate zone, but we’ve found great success with these hardy species, some of which can tolerate cooler temperatures:

• Variatus platies
• Wild type endlers
• Cherry shrimp
• Ricefish
• White cloud mountain minnows
• Killifish
• Japanese trapdoor snails
• Koi and goldfish
• Apistogramma dwarf cichlids
• Rainbowfish

You can even put multiple species together, as long as they’re all peaceful and won’t eat each other. Most fish breed readily outside, so make sure to have an exit strategy in terms of where to keep all the babies. Selling the extra fish and plants to friends, fish stores, or online auctions at the end of pond season can be a nice way to recoup some of your summer tubbing costs.

Livebearers are a common fish to breed during pond season because of their healthy appetites and high birth rates.

How Do You Protect Your Pond From Predators?

Unfortunately, by putting little fish out in nature, you’re also providing potential food for the local wildlife. Cats, raccoons, and larger birds are happy to get a free meal wherever they can. If you don’t have any bigger fish in the mini pond, dragonfly larvae can find a way to sneak in and catch some baby fish. There’s no foolproof protection, but here are some methods to try, depending on which animals you’re having trouble with.

The first line of defense is to provide plenty of hiding spots for the fish using plants, PVC pipes, plant shelves, hardscape, and other decor. Some people put “lids” on top of their tubs (e.g., metal wire racks or greenhouse siding) that still allow light to pass through while keeping predators out. Others prefer to use netting, a grid of clear fishing line, or mesh covers that can be easily removed for your enjoyment.

If you see a strange alien swimming in your pond, it might be a dragonfly larva predating on fish fry.

How Do You Winterize a Small Pond?

Most tropical fish cannot live outdoors during the winter seasons, so drain the water and bring them indoors when temperatures start dipping below 65°F or 18°C. (If you want to keep the fish out longer, consider using a heater to add an extra month of pond season in the spring and fall.) For perennial plants that will come back next year, cut back their leaves to begin their dormant period and store them in the garage or underneath the overturned pond container.

If you want to try keeping cold water fish outdoors in the winter, use a small air stone or sponge filter to keep the water somewhat aerated and allow sufficient oxygen to reach the fish.  If the tub is large enough or buried inground, stratification may occur, such that the surface ices over and insulates the warmer water at the bottom where the fish are “hibernating.” Smaller containers with fish can be moved entirely into the garage to decrease the chances of freezing.

Inground ponds stay warmer in the winter but require extra precautions like safety fences to keep out small children and pets.

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