5 Algae Eating Fish For Your Garden Pond

Excessive algae growth in the pond is not only a visual problem, but also causes sometimes significant problems within the mini-ecosystem. In addition, the green plague is difficult to remove, which is why many a pond owner is only too happy to resort to the support of algae-eating fish. To find out which commonly offered species actually eat algae and which do not meet this expectation, read our article.

Pond fish as algae eaters

Sometimes, however, all precautions and the most beautiful planting do not help. In this case, the five fish species listed here do well both as algae killers and as ornamental fish in the garden pond. However, even with these species you should not expect that they will completely eliminate the algae growth and that the water will become clear again by itself: This is not possible even with algae destroying fish. Here, too, only a combination of eliminating the cause, suitable pond planting and well-considered fish stocking will help.

Grass carp (Ctenopharyngodon idella)

The large and heavy grass carp are very suitable for algae control, because they feed exclusively on algae and other underwater plants. But be careful: due to their size, they are only suitable for really large garden ponds. Also, make sure the planting is very lush, as these fish are voracious and will happily eat ornamental plants or riparian planting if food is scarce. Feed with freshly cut grass if needed.

Size / length: up to 120 centimeters, up to 40 kilograms in weight.
Food: aquatic plants, algae
Reproduction: from temperatures of 20 °C, reproduce very quickly
Pond size: at least 20 square meters per fish
Water quality: high oxygen content, good for this are waterfall, fountain and / or brook run

Moderlieschen (Leucaspius delineatus)

The native Moderlieschen is also an algae-eating fish species with an almost gigantic appetite. The small, silvery fish are also easy to observe, as they usually swim just below the surface, like to hide among the water plants and occasionally hunt mosquitoes buzzing just above the water surface.

Size / length: up to about 10 centimeters
Food: phyto- and zooplankton, algae, mosquitoes
Reproduction: water temperatures above 18 °C, egg laying on
water plants
Group size: schooling fish, at least 10 to 12 fish
Pond size: at least 2000 liters
Pond depth: at least 80 centimeters (for overwintering! Pond must not freeze through)
water quality: high oxygen content, low nitrate content

Rudd (Scardinius erythrophthalmus)

Rudd are also busy algae eaters and therefore well suited for the destruction of algae growth. However, these pretty fish are also very fond of eating other aquatic plants, which is why such a population is quickly decimated and, with a bit of bad luck, you will no longer have any plants in the pond. The best way to prevent this is with regular feeding and preferential planting of aquatic and riparian plants with leathery, broad leaves. Rudd prefer delicate, fine-feathered plants.

Size / length: 20 to 35 centimeters
Appearance: red back, red fins
Food: insects, zooplankton, small invertebrates, aquatic plants, algae
Reproduction: in shallow water (about 20 centimeters deep)
Pond depth: at least 70 centimeters
Group size: at least 5 pieces, at best 10 to 15 pieces

Water quality: oxygen-rich, light current, filter and pump necessary
Tip: You can estimate the water quality based on the dorsal and fin coloration of the rudd: If the water quality is good and the water is rich in oxygen, the red coloration typical for the species will be particularly strong. However, it fades when the water quality is poor, which should be taken as an alarm signal.

sensitive fish then die quickly, and algae growth is also promoted.

Silver carp (Hypophthalmichthys molitrix)

The silver carp, which grows up to one meter in length in the wild, has become quite a problem in some waters due to its voraciousness. Once released for algae control, it also eats other aquatic plants when food is scarce – resulting in bare lakes and ponds and a consequent lack of oxygen. So always make sure that the quaint emitting fish has enough to eat at all times and supplement feeding if necessary.

Size / length: up to 60 centimeters
Food: phytoplankton, good algae eater
Group size: at least four animals
Pond size: at least 20,000 liters
Pond depth: at least 80 centimeters, better more
Water quality: high oxygen content, stagnant to gently flowing water
Pennant carp (Myxocyprinus asiaticus)

Native to China, the pennant carp – sometimes referred to as batfish due to its characteristic appearance – is also a very good algae eater. However, like all carp, it is only suitable for large garden ponds and also has quite specific water quality requirements. Unlike many other pond fish, this species needs water that is as clean as possible, low in nitrates, and has a slightly acidic pH. If you want to keep pennant carp, you should make sure that these requirements are met, otherwise the animals will quickly become ill and die.

Size / length: usually 40 to 60 centimeters, in exceptional cases more.
Food: phytoplankton, good algae eater
Group size: at least five animals, good to socialize with Koi
Pond size: at least 20,000 liters
Pond depth: at least 80 centimeters, better more
Water quality: high oxygen content, water low in nitrates, pH slightly acidic to neutral
Alleged algae eaters in the garden pond
On the Internet as well as in stationary specialized trade, different fish species are advertised as ideal “algae eaters”, which would keep the garden pond free of annoying algae and thus the water clear and clean. Unfortunately, while this is a nice pipe dream, it doesn’t work in practice. Some of the “water-cleaning” fish hardly eat any algae or are not suitable for the garden pond at all, because they need completely different living conditions.

These fish species are considered to be algae-eating, but for various reasons they are not at all:

Nose (Chondrostoma nasus): is native to (strongly) flowing waters.
Golden minnow (Pimephales promelas): eats mainly insects, water fleas, small crustaceans
Common gudgeon (Gobio gobio): eats crayfish, worms and other small animals from the bottom of the pond.
Tip: The best way to keep your garden pond free of algae is to combat the causes of algae growth. These include, above all, a high nutrient content of the water (e.g., fertilizers washed up by seepage from the neighboring lawn) and a high water temperature. The latter can be avoided by shading the water surface, for example, with the help of taller-growing aquatic and riparian plants.

What else helps: mollusks and crustaceans

Besides fish, water snails, pond mussels and native crustaceans also like to eat algae. Especially these species are often kept in the garden pond for this purpose:

European freshwater shrimp (Atyaephyra desmaresti).
Small swamp snail (Galba truncatula)
Posthorn snail (Planorbarius corneus)
Pointed mud snail (Lymnaea stagnalis)
Swamp cover snail (Viviparidae)
Pond mussel (Anodonta cygnea)

But be careful: these little animals reproduce very quickly in good conditions, which can quickly lead to a lack of food. As a result, they vigorously eat not only the unwanted algae, but also other desirable aquatic plants. Therefore, you should not let the stocking become too large and, if necessary, fish out excess snails.