This tutorial is intended to guide you through the process of building an outdoor pond for turtles. It covers everything from the construction of the pond such as location, shape and size, lining options, and filtration and water quality; essential environmental elements such as basking options, water oxygenation, food options, and fencing and protection; to hibernation requirements and preparation.
There are a variety of options for choosing a pond lining. A stock tank, a preformed pond, a pond liner, or even a child's wading pool can be used. Stock tanks may have a drain, called a bulkhead, built in to make cleaning and water changes easier. A preformed liner is great for turtles, as it cannot be punctured by your turtles nails. A flexible pond liner is also an option, however it needs to be a heavy duty liner of 40 mil EPDM (60 is best) to prevent punctures and tears. This method is often preferred as it it has the flexibility of forming the pond in any shape, size and depth of your choice.
Preformed Pond Liner
EPDM 40 mil Liner
Pond Size / Shape
With turtles - Bigger is better. If you are designing a pond specifically for aquatic turtles, then it should be at least 200 gallons. If keeping a varied, natural pond with a mix of animals (turtles and fish as well as other animals), the pond should be in the 1000-3000 gallon range. The size serves more than just adequate room for the turtle, but is necessary to dilute the impurities and waste produced by the turtle and other animals.
The pond should have a variety of depths and should slope gently to provide ease of access. The deepest part of the pond should be at least 3 feet deep. A shallow area will also provide a differential temperature as it warms up under the sun more readily than the deeper end. For daily resting and warming, there should be areas only a few inches deep so the turtles can keep his body submerged while keeping his head free to breathe while resting. If you plan to keep the turtles outside year round in cooler climates, they should have a spot that is at least three feet deep and 18 inches below the frost line. for hibernation (see Hibernation, below).
We suggest allowing a small ground area all around the pond to allow the turtles to bask, investigate, and lay eggs. However it will need to be surrounded by a wall or fencing (see Fencing, below) . Hatchlings and smaller turtles will be viewed as prey by large birds (particularly herons), so they should not be released into open pond areas.
Location / Climate / Temperature
Depending where you live, putting an aquatic turtle outdoors might be something you can only do for a few months in summer. You'll want to pick a large area that allows at least part of the pond to have direct sunlight (facing south) so that the turtles can bask and regulate their temperatures. Along with location, you need to consider the natural range of the species you have. For example, red eared sliders are quite hardy and adaptable. They prefer deeper water, while some turtles prefer to be in shallower or warmer water, so again consider the natural habits of the turtle species when planning your pond. In warmer climates aquatic turtles may be able to live outdoors year round. A variety of slopes and depths will allow the turtles to effectively regulate their temperatures. The difference may only be 1-2 degrees, but will be noticed by the turtles.
In order to avoid anoxia (oxygen starvation), it is vitally important that the pond is adequately oxygenated at all times. The pond should also have a relatively large surface area to provides adequate oxygen levels in the water. Ponds which are deep, but which lack surface area, can result in dangerously low levels of oxygenation - especially during the hot summer and freezing winter. In outdoor ponds, hardy turtles will hibernate during the cold winter months. While hibernating turtles do not surface to breath air, but instead absorb oxygen through their skin. Unless you are absolutely certain that your pond is entirely suitable it is usually much safer to over winter the turtles indoors in properly heated tanks. Water oxygenation can be improved using waterfalls, fountains, and external filters.
Basking is vital to a turtles health, and the pond should have multiple basking areas. Throughout the day as the sun moves, there should be a basking area in the sun at all times. Basking areas can be created with logs, bricks or rocks. Arrange your basking area so it is partially submerged so your turtle can easily get out of the water onto the basking area.
Keep in mind turtles can do a lot of damage to aquatic plants (both by eating them and swimming around them) so if your pond plants are a source of pride adding a turtle to your pond might not be the best idea. However in addition to food, water plants provide shade and shelter and are a great addition to turtle ponds. Anacharis, Duckweed, Frogbit, Pennywort, Water Poppy Water lettuce, water hyacinth, fairy moss, Wendti, Java Fern, Sword , Anubius, and Plantain are recommended.
One great advantage to larger ponds is that you can add feeder fish for your turtle. Turtles will eat (or really try) anything placed it its environment, so ornamental fish such as Koi is discouraged. It is somewhat individual, as some well-fed turtles won't bother chasing fish, while others have a stronger hunting instinct. Be sure to have a wide variety of food available for turtles - while keeping their species in mind. A variety of plants, fish, snails and crustaceans would serve as a healthy diet for your turtle, as well as help naturalize the pond.
Landscaping / Decorating
Aquatic turtles need places to hide both in and out of the water so that they can get away from predators and each other. Hideaways also allow the turtles to regulate their temperature by moving to warmer or cooler locations during hot and cold spells. During the summer, they must have an area of shade to get out of the sun. Common hiding places include thick vegetation, large flower pots on their sides, hollow logs, and other similar hideaways. Water plants provide shade and shelter as well as extra food so are a great addition to turtle ponds. Keep in mind turtles can do a lot of damage to aquatic plants (both by eating them and swimming around them) so if your pond plants are a source of pride adding a turtle to your pond might not be the best idea. Marginal plants like dwarf cattails, dwarf rushes and dwarf papyrus also help naturalize the pond edge.
Fencing / Predator prevention
Turtles are excellent climbers and are adept at escaping, so good security around the pond area is vital. The fencing is use to keep turtles in, and also to keep predators out. Turtles, especially hatchlings will fall prey to raccoons and birds (especially herons). The pond must be enclosed on the sides and the top as turtle-eating birds will come from above (and animals like raccoons that climb fences). The area should have a cement or brick wall, the height being t 2.5 times the maximum carapace length and topped with a screen or wire mesh. Screens block UVB, so make sure the holes on the screen are no smaller than ¾" to ensure proper UVB exposure. Wire mesh should not be used on lower levels as the turtles claws could become stuck or injured, and their delicate noses abrade rather easily. Another 6 to 10 inches of fencing should be buried underground as most aquatic turtles will dig. Climb barriers may be necessary for turtles that can climb the fence or the corners. Stinkpots and wood turtles are two species known to be able to climb many feet up a fence. An ideal fence would be vinyl or PVC coated hardware cloth (rabbit wire) over a frame of pressure-treated wood. If a gate is installed, be sure to bury a board under it to prevent digging out.
If you would rather not have a run and fencing, there should be a shear cliff at least a foot high around the water. This could be accomplished with a rock wall or simply not filling the pond anywhere near the top. One can also make a stone overhang of the pond of at least 4 inches and then have the water at least 5 inches below that to keep the turtles inside. It becomes extra important without land to provide logs, rocks, etc. for the turtles to haul out and sun themselves. Many people make an island of rocks, Styrofoam, or other materials in the middle of bathtub sized ponds. Larger islands in larger ponds require some ingenuity. Aquatic turtles need to get out of the water. More than just basking, females need a sandy or dirt site to lay their eggs (like chickens, females lay eggs, fertilized or not). Sometimes, the turtles want to walk around and investigate. The larger the run, the better and more natural it is for the turtles. Due to the effort and costs of fencing, it is more realistic to provide from 1 to 4 feet of ground away from the pond on some or all sides from the water.
Filtration / Water Quality
Contrary to some people's beliefs, water turtles are affected by the same chemicals in water as fish. These include ammonia, nitrite, nitrate (high levels), low oxygen, pesticides, herbicides, etc. Thus, their ponds should have a good filtration system. This is especially true since, just like fish, aquatic turtles do most of their eating and defecation in the water. An especially good filter is needed. While an ordinary pond can do with an entire water turnover in two to three hours, a turtle pond should have turnover every half hour or so and be rated for twice the size of the actual pond. There should be a good pre-filter like a sponge or floss. This will need to be cleaned as often as it clogs, perhaps daily. The biological filtration should be adequate to keep ammonia and nitrite levels undetectable. An example setup might be a Pond master 700 (700 gph pump) in a 200-400 gallon pond. Remember, a 700 gph pump only pumps at 100 gph if it is old or clogged. If you can change about 10-20% of the water every week or two, that should be adequate if you do not have a heavy bio-load. The filter itself should be substantial and rated for twice the size of the pond. Turtles are particularly dirty and require superior filtration.
There are three types of filtration: Mechanical, chemical, and biological. Mechanical filtration is basically just like a strainer. All it does is take out the solid pieces. Chemical filtration is usually just active carbon and acts like a Brita or Pur filter by absorbing toxins from the water. If chemical media isn't changed regularly it will eventually begin to release what it has absorbed and you will see a spike in the toxin levels in the tank. We recommend biological filtration. Basically, biological filtration is the natural breakdown of waste through the Nitrification Cycle. The Nitrification Cycle is what occurs in your filter that actually "cleans" the water. Understanding this cycle is an important step in the care of any aquatic animal and will help you keep your water cleaner, and along with saving you money on inappropriate filters/filter equipment, and also serve you well incase of a filtering emergency.
As your turtles, fish, etc expel waste it builds up in the water as ammonia. Initially there will be a pretty good spike in the ammonia level. 20% water changes every day or two should help keep that under control until the water "cycles". As the ammonia rises aerobic bacteria (aerobic bacteria utilize oxygen and a "food source" for energy" like we do) begin to colonize in the porous surfaces of the filter media where the water flowing through brings them more food (ammonia) and oxygen. Because of the plentiful food source (the spike in the ammonia levels) the bacteria population has a tendency to explode to the point of making the water cloudy. As the bacteria "eat" the ammonia the ammonia levels drop and the bacteria expel nitrites. Now you will see a spike in the nitrites as the bacteria break the ammonia down into nitrites. It's now that second type of aerobic bacteria take hold in the filter along side the first. These bacteria utilize the oxygen and nitrites in the water and produce nitrates. So now both your ammonia and nitrite levels will drop and should maintain at a nice low level. However, you will have a steady increase in the levels of nitrates. Nitrates are less toxic than either nitrites or ammonia and is tolerated better. However, no aerobic bacteria utilize the nitrates as food. That's where the 20% water changes come into play. The water changes are actually to reduce the nitrate levels. An interesting note is nitrates are good fertilizers. So high nitrate levels will promote algae and pond scum growth. At the same time live plants could help control nitrate levels a little but no turtle can resist tearing up all the plants. The waste water is great for gardens though or for growing your own aquatic plants in a separate tank.
Hibernating - Requirements & Preparation
Many aquatic turtles from temperate climates (including red eared sliders) hibernate during winter months. You should only try hibernating species that are native to your area or colder climates. Hibernation generally occurs when temperatures fall to about 50 F (10 C). The pond is deep enough that in the coldest winter in history for your area, there will still be a foot of unfrozen water under the ice. For example, in Zone 6-7 the pond must be at least two feet deep with three feet being much better. In colder regions, it should be even deeper. The most important thing is that there needs to be an additional 18 inches below the frost line (you can determine your area's frost line by contacting your local agricultural society) of sediment or material such as leaves, mud, or dirt for the turtle burrow into to prevent freezing. Too much decaying plant matter can negatively impact water quality though, so be careful about having too much. Proper oxygenation is essential during hibernation. A hibernating turtle needs at least a foot of water that isn't frozen at the bottom of the pond. The pond must also have a large surface area, to facilitate sufficient oxygen levels in the water. When the turtles have settled into the sediment at the bottom of a pond to hibernate, they switch to absorbing oxygen through the skin, so the levels of oxygen in the water must be sufficient. It will come up a few times on warm days to breathe through its lungs but if the pond is mostly frozen, the turtle cannot surface. In addition to requiring high levels of oxygen in the water over winter, the turtle needs low levels of carbon dioxide, hydrogen sulfide, and methane. The carbon dioxide is expelled by all animals in the pond. The hydrogen sulfide and methane are released as plant material, dead animals, etc. decompose in the water. The pond should have some sort of water movement occurring during winter. The aerated water will add oxygen and release the carbon dioxide, hydrogen sulfide, and methane. If the pond cannot "breathe," these gases can prove deadly for any and all animals in the pond. A little debris (large leaves mostly) is advantageous for the turtle to hide under or dig into (if you have a clay-bottomed pond or some mulm which is small pieces of leaves and decomposing stuff). Total freezing of the surface in winter can be prevented by using submersible pond-warmers. These and many other accessories can be found online or obtained from local pond centers and aquatic mail order suppliers. The catalogues issued by aquatic supply companies can provide a wealth of interesting ideas and often contain many useful items which used imaginatively can greatly improve the quality of a captive turtle's life.
Preparation of your turtles health is essential to successful hibernation. Hibernating turtles can be a risky proposition and some experts believe that hibernating aquatic turtles outdoors is too dangerous due to the difficulty of replicating a ponds natural conditions and advice against outdoor hibernation. If you do decide to try hibernating aquatic turtles, there are several important things to consider. You must be absolutely certain your turtle is healthy and strong before even considering outdoor hibernation. The turtle has had time to get used to the change of seasons and has been in the pond at least since mid-summer. Place your turtle in a pond in the warm months such as June or July, do not do it any later because than the turtles have not enough time to get used to the cold before the winter comes, and it might be freezing at night. As the days grow shorter and colder, the turtles and any other animals in the pond eat less and less. As temperatures approach 50 F (10 C), the turtle stops eating and they should not be fed for about a month or so before hibernation to allow the digestive tract to empty before they go into hibernation. Any food left in the stomach during hibernation will decompose, often killing the turtle.
Outdoor hibernation is not suitable for hatchlings or juveniles. Hatchlings should be housed indoors in heated tanks until they have attained a reasonable size. Unless you prefer to leave nature to take its course, it is not usually a good idea to hibernate a hatchling its first year. Hatchlings born too late in the year (October or later) may not survive their first winter because they have not had enough time to gain enough weight to sustain them during the winter or find a suitable hibernation spot.