Phylum — Mollusca.
Class — Gastropoda.
Superfamily — Planorboidea.
Family — Planorbidae.
Genus — Planorbis.
Great Ramshorn Snail.
Family Planorbidae. This family is the largest among freshwater snails and is widely distributed worldwide. The family Planorbidae includes 3 subfamilies: Rhodacmeinae, Buliniae, Planorbinae. Most Planorbidae have a flat shell somewhat similar in shape to ram horns, commonly known in English as ramshorn snails. In warm-water aquarium hobby, great ramshorn snails are primarily known. The snail can be distinguished at first glance due to its extremely characteristic shell coiled in a single plane like a spiral cord.
The most common in aquariums are the great ramshorn snail, keeled ramshorn, vortex snail, and white ramshorn. In most cases, you don’t need to introduce them into the aquarium; one fine day they just appear there by themselves. Despite alum baths for plants and all other precautionary measures, these creatures find ways to enter our aquariums and multiply inside them.
In nature, ramshorn snails, like pond snails, are carriers of dangerous parasitic fish diseases — trematodiasis. As long as their population remains within limits, they cannot cause harm. But if, due to any special circumstances, their mass reproduction begins, the situation worsens. Under conditions of chronic starvation, these snails do not disappear, they just become much smaller. Most often, the aquarist fights the invasion independently by collecting larger specimens from the bottom and plants and removing them from the aquarium.
Among medium-sized snails, we can note the marginate ramshorn (P. marginatus) — shell diameter 15 mm, thickness 3.5 mm, whose whorls are equipped with a thread-like keel running in the middle of the whorl. Much more common than the previous one is the keeled ramshorn (P. carinatus), almost of the same size, in which the thread-like keel is shifted to the lower side. Slightly smaller is the vortex snail (P. vortex) — shell diameter 10 mm, thickness 1 mm, very flat shape, with tightly coiled whorls, with a keel without a thread-like appendage. Shells of P. complanatus — shell diameter 4-5 mm, thickness 1.8 mm, whose whorls are very tightly coiled, numbering up to 7-8.
— Planorbis polypylus — Far Eastern Ramshorn. Family Planorbidae. Found in the swamps of East Asia. The shell is red-brown, obliquely incised with thin stripes, having a convexo-concave disk shape. There are 5 to 6 whorls, located in a slow upward spiral line. The aperture of the shell is narrow, strongly elongated forward along the upper edge, heart-shaped. The shell of an adult specimen does not exceed 10 millimeters in diameter and no more than 3.5 millimeters in width. It adapts wonderfully to home aquarium conditions, is quite undemanding, and feeds on all types of aquarium algae.
— Planorbis planorbis [Linnaeus, 1758] — Keeled Ramshorn. Family Planorbidae, subfamily Planorbinae. Inhabits both permanent and temporary stagnant or slow-flowing water bodies mainly in Central Asia, Siberia, and Europe. The snail’s shell is durable, translucent, with a grayish-brown color. Spiral whorls usually number 4 to 5; a distinctive feature of this snail’s shell is that the whorls are much wider than they are tall, with a well-defined suture and slowly growing upwards.
The shell diameter does not exceed 2 centimeters, while adults do not reach a height of more than 4 millimeters. The soft body and foot vary in color depending on the region of origin, ranging from dark gray to light pink and from red to dark maroon. Like most gastropods, it feeds on bottom sediments. In the aquarium, the snails clean plants and aquarium substrate from algae (not all types).
Hermaphrodites, very prolific and breed successfully at home. It should be understood that excessive population growth of Planorbis is always associated with an excess of nutrients. Introduced with plants, the small invertebrate eggs are transparent and difficult to detect.
Genus — Gyraulus.
— Gyraulus acronicus [A. Ferussac, 1807] — Snail. Synonym: Gyraulus gredleri, Planorbis acronicus, deformis. Family Planorbidae. Native to various parts of Europe, especially southern and eastern regions. The shell is quite thin, almost transparent, shaped like a flat disk with a diameter of 5 mm and a body thickness of 2 mm, with 3.5 to 4.5 whorls. Specimens with slightly larger sizes are rare. If drastic environmental changes (especially water hardness) occurred during the growth phase, the number of whorls may be fewer, and the shell may exhibit various deformations.
The shell color varies from brown to gray and copper, with different shades depending on water quality. Body coloration is usually purple, sometimes brownish or beige, with a narrow foot. On the sides are two narrow and long head tentacles, at the base of which the eyes are located. The mouth is very small, but efficient with a radula. They move holding their shells horizontally, but with the ventral part facing up rather than down.
Very peaceful, form groups on their own due to rapid reproduction. They move rather slowly, keeping the body parallel to the supporting surface. They are very useful in the aquarium as they remove waste from the bottom and plants. They feed mainly on algae and plant residues. Excessively acidic water damages the shell, which consists of calcium carbonate. pH 7.0-7.5.
Due to their small size, their shell usually does not dissolve as easily as that of other relatives, so they can often be seen in aquariums with soft and acidic water. In acidic waters, reproduction is more limited. Temperature from 22°C to 28°C. At excessively low temperatures, they become inactive. They live from 1 to 2 years.
Superfamily — Acroloxoidea.
Family — Acroloxidae.
Genus — Acroloxus.
— Acroloxus lacustris [Linnaeus, 1758] — Lake Fingernail Snail. Synonym: Ancylus lacustris. Another member of our freshwater pulmonate snails is the small river limpet (Ancylus). These snails are found in ponds, on plants, or on stones in shallow water. Maximum size is 2 cm. The shell of this snail is saucer-shaped, somewhat resembling a Chinese hat, with faint traces of a spire and an apex turned to the left. The shell is extremely fragile and breaks at the slightest touch.
Its color is transparent yellow-brown on the outside and white on the inside. It can have gray, brown, cream, or pearly colors. The animal’s body is yellowish-gray, transparent, with black eyes. The body fills the entire shell so that only the tentacles protrude beyond the edge when the mollusk crawls, and these tentacles are very small.
The limpet is a very lazy, sluggish animal, crawling mostly on submerged plants, trying to get closer to the water surface, sometimes right next to the filter outlet, near which it usually lies attached to a plant. Good oxygen saturation of the water is required. They need good water quality for successful reproduction, being very demanding regarding oxygen levels and hardness (they dislike soft and acidic water).
Similarly, they react negatively to increases in nitrates, nitrites, ammonia, and heavy metals. They tolerate low temperatures; the optimal temperature is 20-22°C. They feed on microscopic algae growing on plants, rocks, and substrate. They lay eggs in the form of a star-shaped jelly-like cluster, containing a very small number of eggs (no more than 4-6 pieces).
In addition to A. lacustris, a related species Ancylus fluviatilis is also found here, differing mainly in that the apex of the shell is turned to the right, as well as having a black-gray body and longer tentacles. This species is found only in flowing water, mainly in streams, on piles and stones. The animal is just as sluggish and slow as A. lacustris.
Planorbis (Planorbarius) corneus + var. rubra.
Apple Snail, Pomacea bridgesii, maculata, canaliculata, Asolene spixi. 
