Creation of a two-level pond

What could be more pleasant than a corner of water in the garden near the terrace, which is more animated by the composition of two tanks at two different levels. Through an example of realization, let's discover how to realize the whole.

In this example, the pond is composed of two large rectangular tanks built into each other. The first, high tank is the largest volume of water. The second, lower level, is nested in a corner. At the back there is a planter and a technical room.

The upper pond

The upper pond is the largest volume, the height of the edge corresponds to the height of a bench to sit at the water's edge.

It receives the filtered water in the back left corner and has two overflows in the front right corner, consisting of two tubes that return the water to the lower pond. Thus, the level of the upper pond does not vary. On one of the overflows a vertical suction pipe for the bottom water is fixed. In case the overflow gets blocked, a gutter is placed in the corner to ensure an emergency overflow. 

A drain is provided at the bottom of the high pond towards the garden. This is closed by a plug.

The low pond

The lower square pond is placed in front of and partly embedded in a corner of the upper pond. It receives the water from the upper pond and acts as a buffer by absorbing the variations in water level due to evaporation. An overflow towards the garden is installed at the back right in case of excess water following winter rains for example.

At the bottom, a tube connects the pond to the technical room to connect the water circulation pump.

The technical room

The technical room of the installation is placed behind the low pond. An electrical area with a bar of waterproof plugs is provided as well as the arrival of the piping bringing the water from the lower pond. It receives the filter and the lighting of the pond.

The pump is calculated to circulate the total volume of water in a little less than an hour. In our example the volume is about 4m3 and the pump 5.5m3/h. The pump will be slowed down by the length of the pipes and especially by the filter.

The filter is sized accordingly. It is equipped with an ultraviolet lamp to prevent the development of green algae.

A waterproof lighting system is installed to illuminate the bottom of both ponds.

The plants

The deep pond will host a water lily and floating plants. Beware of the obstruction of the overflows by these plants.

The lower pond with its shallower depth will host tall plants such as marsh iris or horsetail, lower perennials such as water marigold whose pots will be enhanced by a cinder block and submerged plants such as milfoil. 

The plants are planted in pots with holes filled with a potting soil for aquatic plants with a thick layer of pozzolan on top to prevent the soil from going into the water and the fish from stirring up the soil by digging in. 

Getting started

Take advantage of the fall and winter months for the work and prefer early spring for the start-up of the pond. The sun is not yet too strong and the heat is not too great, so it is a good time to start and install the plants.

Which pond for the sturgeon?

Majestic fish with shapes reminiscent of prehistoric monsters, the sturgeon is not suitable for all ponds, far from it! Before acquiring one, it is better to be well informed...

To better know the sturgeon

The common sturgeon (Ascipenser sturio) is an impressive fish that can reach more than 3 meters in length and weigh 300 kg. This species is part of the CITES list and is therefore fully protected because it is in decline. These fish used to populate the rivers of Northern and Western France in large numbers. Other species are included in the CITES list.

Only authorized species are commercialized, including some hybrids dedicated to this purpose and bred only for this purpose. Others, such as Ascipenser transmontanus, the white sturgeon, are very difficult to obtain. The latter is native to the great rivers of the American West. Its rows of white bony blades (scutes) on the back and on the sides make it a very ornamental subject. All species have these scutes, as well as an elongated head covered with bony plates ending with 4 barbels around the mouth. The color varies from light brown to dark gray, with lighter sides and an often white belly.

The sturgeon is a benthic and migratory fish, it can live up to 15 years in fresh water but feeds in the sea once adult. It will then return to the estuaries to reproduce. It is for its unfertilized eggs that the female is killed, the population was thus gradually decimated, to produce the famous caviar, so appreciated at the tables of great restaurants and essential on yachts.

Is my pond suitable for a sturgeon?

To introduce a sturgeon into your home, it is better to speak of a pond or a small lake than a pond! This highly developed fish needs a lot of space to grow harmoniously. As we have seen, the beast can happily exceed 3 meters in length, and even if the salesmen will tell you that a fish adapts to the size of the pond, they often forget to specify that it is to the detriment of its life span and its well-being!

It is therefore useless to introduce a sturgeon into a pond whose size will not exceed 25 m² and whose depth will not exceed 80 cm.

Did you know that?

Sturgeons only feed at the bottom of the pond and this, throughout the year, unlike most other pond fish that overwinter.

Think about them during the bad season and do not stop feeding. There are specialized pellets that sink directly to the bottom to feed them.

Feeding your pond fish

Feeding your fish seems like a simple thing to do, and yet! Feeding is often the cause of many problems in the pond. Let's learn how to feed your fish wisely to preserve their health and the balance of the water.

How to feed your pond fish?

Always buy the right food for the species in your pond. Some fish feed on the surface and will be satisfied with floating food, others, such as sturgeon, are bottom dwellers and will therefore need food that sinks directly.

Be careful with the amount of food given, which is often too much; a tip is to check that all the food is absorbed within 5 minutes. If the food is given in excess, it will end up soiling the pond water. This can lead to problems with filtration, pollution and invasive algae. If the water is polluted, or if the nitrate level is too high, the fish may suffer and be more susceptible to various diseases.

In summer, some fish feed on mosquito larvae and need less food. This means savings and fewer mosquito bites!

Some fish are also fond of aquatic plants such as duckweed, this should be taken into account when feeding.

When to feed pond fish?

Pond fish do not all have the same needs because some of them go into a resting period during the winter, so food will only be distributed very sparingly. Sturgeons are still an exception as they are well adapted to the cold and remain active even in winter, so you should continue to feed them very regularly.

Generally speaking, as soon as the temperature drops below 8°C, it is useless to feed the majority of the pond fish, which will then become lethargic. The water would be unnecessarily contaminated and the transit of the fish would be disturbed by this superfluous food supply.

When the temperature rises in spring but does not exceed 14°C, gradually start feeding your fish once to three times a week.

When the temperature rises above 15°C, you can start feeding daily. If the night and day temperature is above 21°C you can feed them 3 times a day especially during the breeding period and when there are fry. The food given to small fish should be specific because it is very rich and digestible.

Pond fish

If the installation of fish in a pond requires some minimum precautions, in practice success is very often at the end of the road! Here are some tips for a lively pond!

The creation of an outdoor pond often aims to install a flock of fish that will give life and color to the stagnant water. To facilitate the success of this project, a few tips are important to remember.

First of all, the water must obviously be clean! The use of pesticides or fungicides should be avoided in the vicinity of the pond!

The second main principle to ensure a serene life for your fish is to encourage the installation of insects. The planting of aquatic plants will encourage the arrival of this providential guard provided that a space in shallow water is provided where the larvae can develop without having to suffer from the attacks of the fish!

Generally, it takes a good month between the time the pond is dug and the introduction of the fish so that the pond is populated with sufficient microbial fauna for a harmonious biological balance. When all the ingredients are present, it is time to look for new residents. And there, the choice can be difficult!

Indeed, not all fishes agree! Some of them eat each other while others live together quietly. To be sure of your choice, it is better to avoid mixing species.

For smaller ponds, the best choice is undoubtedly the goldfish. These small fish (maximum 40 cm) live perfectly in schools. The species has many varieties: red, black, orange and white, with simple fins or undulating fins (the comet).

For larger ponds, it is possible to choose a mixture of goldfish and Koi. These two species cohabit perfectly if there is enough space. Be careful though: Koi carp are imposing. It can reach up to more than one meter in length which implies to calculate the number of fish per cubic meter!

Other possible species of pond fish are the sarasa (20 to 23 cm) which is characterized by its red back and white belly or the shunbukin (20 to 23 cm) which can be recognized thanks to its multicolored blue, black, red, orange and white body, the ide (35 to 50 cm) with its bright orange back or the tench (30 to 60 cm) with its pretty green dress.

The water birds of the pond

The reception of water birds, whether wild or domestic, requires prior preparation of the pond. A few simple arrangements are necessary to facilitate cohabitation and maintain biodiversity.

When creating an ornamental or swimming pond in the garden, the first reflex is to create an "ideal" space for the fish without necessarily worrying about the birds.

This is a mistake, because it is obvious that even if domesticated waterfowl are not allowed, the pond will inevitably attract wild birds.

Indeed, a watering place is often the place where many birds converge such as geese, ducks, herons and other swans.  They find there something to drink, but also something to bathe in and something to eat.

To prevent these birds from destabilizing the biotope, a few small adjustments are necessary. For example, by installing wire mesh over the shallow water of the banks, sheltered areas are created for the tadpoles. Without this precaution, the future frogs have no chance of escaping the voracity of passing birds.

If the pond is often exposed to waterfowl, it is also a good idea to cover the shoreline with pebbles or a plastic mat. This protection of the floor in shallow water will prevent silt from forming. When a duck comes along, it will not be tempted to dig for food, which will prevent the water from being contaminated by suspended silt. 

If there are many wild birds, it is also more than recommended to choose large fish species to avoid that they end up as an appetizing meal for the birds. If the pond is to be used for domesticated ornamental birds, the same considerations apply. It is also advisable to add a screen around the pond to prevent the birds from escaping and to prevent predators, such as foxes, from doing their business.

The choice of ornamental bird varieties is immense. 160 species of ducks are domesticated among which we find the mandarin ducks, the shoveler ducks, the gadwall ducks, the whistling ducks, the pintails, the carolins. In addition to these species, there are other birds such as teals, geese, and domestic geese...

All these domestic birds require little maintenance. Depending on the case, a food supply will be necessary, especially if the pond is small. Deworming twice a year helps to keep the birds in good shape and to keep the water healthy.

The insects of the pond, necessary for its balance

The success of a pond in the garden is based on the establishment of a complex ecosystem where insects play an important role since they are, in spite of themselves, a real "pantry" for the fish and amphibians of the pond!

At the slightest water hole, life swarms! If the fish and plants can obviously be put in place by the hand of man, the arrival of the insects is entirely (or almost entirely) the work of nature! And we must admit that nature is well done, since it only takes a few weeks at the most after the installation of a pond to see many species of water flea insects flocking in.

The main purpose of these insects is to provide a food source for the fish and amphibians in the pond. This is true if the pond has been well designed of course! Indeed, to ensure the survival of these insects, you must think of providing them with a small shallow corner that will keep them safe from adult fish. This small attention will also be welcome to provide a shelter for fry and small fragile fish.

Generally, the first to colonize the wetland are mosquitoes. These insects, which are very unpleasant for the fragile skin of humans, are a real godsend for fish, since their larvae, which lie flush with the water, are a king's meal for any well-constituted fish.

Apart from mosquitoes, many other species will gradually colonize the space, including the very graceful dragonflies, but also detritivores, phytophagous, insectivorous predators, not to mention certain exclusively aquatic species such as dytics and water bugs.

All these insects will attract amphibians and birds to the pond. Although all these insects promote biodiversity without compromising the pond's internal balance, some species should be closely monitored, such as the caterpillars of the water lily (a small butterfly) and the water beetle (a small beetle) whose larvae shamelessly devour the leaves of aquatic plants.

The same goes for aphids, which are best drowned from time to time by immersing the infested leaves in water to avoid carnage on the water lilies! With one simple action, the greedy aphids will become a real feast for the fish!

The great variety of insects attracted by stagnant water is a guarantee of balance for the pond. To preserve it, it is obviously imperative to ban the use of pesticides in the garden!