Garden pond: required size + depth for fish - goldfish


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Water lilies nymphaea

There is a simple rule of thumb for choosing the size of a goldfish garden pond: for each centimeter of length of a goldfish, at least three liters of water should be used. For five goldfish, each ten centimeters long, that would be:
  • 5 fish x 10 centimeters per fish = 50 centimeters fish length
  • 50 x 3 liters = 150 liters
What is not considered, however, is the growth of the fish or their final size, a possible increase and the volume of water that accounts for plants. The calculation should therefore take into account the following factors:
  • The first 1,000 liters should be accounted for by aquatic plants
  • Goldfish can become 35 centimeters long, depending on the breed
  • Goldfish spawn contains 500 to 3000 eggs
Although only a small fraction of the eggs can usually be fertilized and hatched, the youth rate can still be quite high. The size of the garden pond should therefore never be calculated only for the currently available fish. It is better to plan the final size of the fish and a reserve for plants and offspring. Also other aquatic organisms, such as frogs, tadpoles and newts should be included. Because these also drop feces and consume the oxygen contained in the water.
The rough calculation might look like this:
  • 5 fish x 35 centimeters length = 175 centimeters fish length
  • 175 x 3 liters per centimeter = 525 liters
525 liters for the current fish stock
+ 1,000 liters for aquatic plants
+ 1,000 liters for potential offspring and other aquatic creatures
= 2,525 liters
That sounds like a very big pond and the reserves are already generously calculated. In fact, with a round pond shape, a diameter and depth of 1.5 meters would be enough to reach this volume of water. The advantage of this generous calculation and the planned reserves, in turn, is that the balance of the water is more stable and thus the cleaning effort is reduced - but the safety is increased.

depth

Water lily - dragonfly

In addition to the circumference, radius or diameter, of course, the depth also plays a decisive role in pond size. For one, it affects the volume of water. On the other hand, a greater depth offers better opportunities for retreating the goldfish and thus protection against enemies. Furthermore, it also facilitates the wintering of the fish. The absolute minimum depth for goldfish is 80 centimeters. In summer, there are still cooler water areas in the depth. In winter, the garden pond can not completely freeze over. Better, however, is a depth of 1.0 to 1.5 meters. Such a depth means at the garden pond:
  • no complete freezing even in cold winters
  • more stable temperatures throughout the year
  • Cleaning and suction of pond mud is still possible
  • greater safety of the fish from predators, such as cats or herons
  • Design of different sections and introduction of different plants possible
When creating the garden pond means a greater depth, although more effort. In the long term, however, there is an advantage in particular due to the safer and easier wintering of goldfish. In addition, the fish can dodge in summer, when the upper water areas are too warm.

Calculate garden pond volume

The bigger, the better - that's clear by now. But how can the volume of water in a garden pond be calculated at all? Because if it is not a perfect cuboid shape and the pond may also have different sections, the calculation seems difficult to impossible. The solution to this, however, is very simple. Not the entire garden pond is calculated, but the respective sections.
In the process, the surface areas of the respective shapes are first calculated and then multiplied by the depth of the section.

Squares and rectangles

For the area of ​​rectangles and squares, only the side lengths are multiplied together.
So:
Side length a x side length b = surface area (A)
1 meter x 2 meters = 2 square meters
To calculate the volume from this, the depth is multiplied by the area.
A x depth = volume
2 square meters x 1.5 meters = 3 cubic meters

circles

For the surface area of ​​a circular shape, the radius or half the diameter is first squared and then multiplied by the number Pi.
Radius² x Pi = area (A)
(0.75 mx 0.75 m) x 3.14159 = 1.76715 square meters
For the volume of the round section, in turn, the area is multiplied by the volume.
Area (A) x depth = volume (V)
1,76715 square meters x 1.5 meters = 2,65072 cubic meters

Ellipses or ovals

For garden ponds, elliptical or oval shapes are often chosen.The surface area is calculated by multiplying half of the axes with each other and with the number Pi. To calculate the half-axes, the two side lengths are only halved.
For a pond two meters long and one meter wide, the long half-axis (a) measures one meter, the short half-axis (b) measures 0.5 meters.
a x b x Pi = area
1 meter x 0.5 meters x 3.14159 = 1.5708 square meters
For the volume, multiply this result as with the other shapes using the depth of the section.
Area (A) x depth = volume (V)
1.5708 square meters x 1.5 meters = 2.3562 cubic meters
Finally, the cubic meters only have to be converted into liters. One cubic meter equals 1,000 liters. A volume of three cubic meters holds 3,000 liters.

Calculate area of ​​pond volume


Tip: However, it should be noted that these are only approximate values, since the pond usually tapers downwards, ie becomes narrower. If you want to make sure that enough water is available for the desired number of fish, you should therefore make the side lengths slightly larger and create a slightly higher target volume.

Pond size and wintering

As large as possible and deep garden ponds provide protection during the hibernation and allow the goldfish to remain outdoors even during the cold season. But there is more to it, because not only the low temperatures put the fish to.
The garden pond is usually designed so that it tapers to the bottom. This also reduces the volume of water in depth. If the pond now freezes from the top, the goldfish not only have less space and water available, but also less oxygen. This in itself is not problematic, because the slowed down metabolism during the winter also slows the respiration of the fish.
But if the number of fish is large, the pond will freeze or consume aquatic plants in the pond. Oxygen, instead of producing it, becomes dangerous. In fact, most fish do not freeze in ponds, instead stifling them. To reduce this risk, complete freezing of the garden pond should be prevented, no matter how big or deep it is. For this the following measure is recommended:

1. For small garden ponds use a thick Styrofoam plate or better still a special Eisfreihalter. For larger ponds, it should be several Styrofoam plates or a Eisfreihalter with air pump.

2. If a Styrofoam plate is used, a hole should be cut in the middle and a piece of garden hose should be passed through. The hose should be so long that it reaches almost to the bottom but not in the ground.

3. In order to prevent the Styrofoam from floating too easily on the water and thus above the ice, weighting may be required. For this purpose, offer heavier, larger stones that are all around easily pressed into the Styrofoam or glued to it. Special weights can also be used.

Tip: Styrofoam or ice protectors should be applied to the pond as early as autumn to provide protection against any early night frost.

Video Board: Pond Depth for Koi & Goldfish Pond Beginners - Koivet Dr Johnson.

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