Eradication of planarians and hydras in a shrimp tank.
There are many aquarium parasites. However, planarians and hydras are the ones that trouble shrimp keepers the most. The fact that the problem of removing all sorts of pests like planarians and hydras from shrimp tanks periodically arises among aquarists is neither new nor sensational. These uninvited guests are extremely resilient. Planarians eat shrimp eggs, juveniles, and some snails. They can also attack adult shrimp during molting or crawl under the carapace of crayfish.
Small whitish-pink worms with a triangular front part are often introduced into the aquarium along with aquatic plants, snails, live, and even frozen foods. In home aquariums, the most common species encountered are Dendrocoelum lacteum, Planaria lugubris, or Planaria torva. They move closer to the water surface and are most active at night, hiding in the substrate and among plants during the day, making them difficult to notice, especially brown or mourning planarians. White-milky planarians reveal themselves faster due to their coloration.
Planarians belong to flatworms. Their average size ranges from 0.3 to 1.0 centimeters. They have two eyes, a triangular head, and varying coloration. Planarians can be white, brown, red, and transparent. They are very flexible and capable of slipping into even the tiniest crevices. Their bodies stretch and contract. If disturbed, they curl into a ring and fall onto the substrate. A planarian cut into pieces will regenerate, and eventually, several new planarians will result from the pieces. The only control measures against planarians consist of removing them from the aquarium with a net or siphon, using shrimp-safe chemical treatments, and preventing their appearance by avoiding overfeeding fish and shrimp.
The main cause of their appearance is overfeeding aquarium inhabitants. Methods to combat this resilient predator are based on its highly developed sense of smell. A small amount of scraped beef is placed in a gauze pouch and lowered into the aquarium on a fishing line, close to plants or the substrate. The aquarium is then darkened. Planarians gather on the bait quite quickly. The pouch is retrieved with a net and plunged into boiling water. The procedure is repeated every few days. Unfortunately, these methods have low effectiveness. Worms that escape capture and eggs left in the aquarium will reduce your efforts to zero in a very short time. Furthermore, it is inconvenient in terms of organic pollution of the aquarium, as such “operations” must be carried out for more than one day.
If females regularly carry eggs but there is no offspring, check the aquarium for planarians! Planarians are true raiders. Neither young crustaceans nor adult specimens, especially after molting, can feel safe. If left unchecked, the entire decapod population could be destroyed in a very short time. Decapod protein-rich eggs are a favorite prey for planarians. But even if you do not aim to breed crayfish and shrimp, stay alert: in search of food, agile worms crawl under the carapace of crustaceans and clog their gills, causing suffocation.
Another common parasite is the hydra (Hydridae). Hydras enter the aquarium with newly purchased plants or any natural object. Hydras belong to the group of cnidarian aquatic invertebrates. Their body is a stalk-like stem by which they attach to any surfaces in the aquarium — glass, substrate, driftwood, plants, and even snail egg clutches. The body of a hydra consists of a longer main part and a thinner stalk, the base of which (the basal disc) is attached to the substrate.
The mouth opening is surrounded by tentacles. The number of tentacles, their length, and position relative to the body vary among different hydra species. All of them possess regeneration capabilities (the ability to restore lost organs). A hydra moves slowly by contracting and stretching its body and tentacles or by “doing cartwheels”. If a fully extended animal is disturbed, its body, which resembles a long narrow cylinder, instantly becomes short and thick, and the tentacles contract sharply.
A hydra uses its tentacles to capture prey. The long tentacles crowning the hydra’s body are in constant motion, catching numerous small, sometimes invisible-to-the-eye creatures from the water and bringing them to the mouth at the end of the hydra’s body. The hydra discharges threads with toxic substances from nematocyst capsules, paralyzing the victim. Like a fisherman with a line and hook, the hydra catches small prey, including crustaceans, with its tentacles and brings it already dead to the mouth opening located on the rounded part of its body. It also feeds on tiny food particles suspended in the water column. It is known that hydras eat fish fry and small shrimp.
Besides a voracious appetite, the hydra’s ability to recover is terrifying. Like planarians, it can recreate itself from any piece of its body; regeneration from the tiniest remnants makes it practically immortal and indestructible. Therefore, crushing them against the aquarium glass is useless. If you carefully inspect plants removed from the water, you may notice small light-brown slimy lumps on them. These are hydras that have shriveled up when removed from the water. Plants must be disinfected before placing them in the aquarium. Hydras live for about a year in an aquarium.
Just like planarians, hydras thrive in dirty aquariums. Moreover, before shrimp became popular in our aquaculture (and the trend for shrimp-only or shrimp-and-fish aquariums), planarians and hydras were not a problem for aquarists: there are quite a few biological and chemical methods to combat these cute creatures, leaving no chance for populations to develop unchecked. But in shrimp tanks, the situation is completely different.
A shrimp tank is the ultimate resort for them. There is plenty of food and almost no risk because, given the sensitivity of shrimp to metals and chemicals, if “military action” begins, they will die much faster than the unwanted guests. A hydra can swim and even attach to the surface film of water, live on it, collect dry food, and catch artemia. Rumor has it that hydras are eaten by Julidochromis, Ancistrus, Bettas, Gouramis (marble and kissing), Macropods, Black Mollies, Swordtails, and large apple snails (Pomacea).
Hydra’s love for light is also used to combat them. It has been noticed that hydras locate closer to light sources. A piece of glass is tightly pressed against the aquarium wall, and a light source (lamp or flashlight) is directed at that spot during the dark hours. As a result, overnight, the hydras relocate to the trap-glass, which is then removed from the water and scalded with boiling water. This remedy is better described as population control since this method does not provide complete eradication of hydras.
In empty aquariums without plants (e.g., quarantine tanks), you can quickly get rid of hydras using hydrogen peroxide. To do this, fish are caught from the aquarium, and 2 teaspoons of a 3% hydrogen peroxide solution are added to the water for every ten liters of aquarium volume. The peroxide is pre-diluted in a glass of water. However, to achieve the proper effect, the hydrogen peroxide solution at a rate of 40 ml per 100 liters of water must be added daily for a week. The generated free oxygen causes such severe burns to hydras that they cannot recover from them. Shrimp and fish tolerate this procedure well, but plants not so much.
There is a medication used to treat worm infestations in various animals: fish, birds, dogs, cats, and livestock. We are talking about Fenbendazol, Flubendazol, Flubenol, Flumoxal. However, you should ensure that the product does not contain copper or any active ingredient other than fenbendazole, otherwise, the shrimp will not survive the treatment. The drug is introduced into the aquarium at the rate of 0.2 (up to 0.4 g) of active substance per 100 liters of water and gradually increased. Before use, the powder should be ground as finely as possible. The drug is poorly soluble, so it makes sense to purchase a ready-made suspension (usually 22.2%) or thoroughly mix it in a separate container.
It is important to avoid overdosing, as it can cause serious problems. At the recommended dose, the medication is safe for Cherry shrimp, Amano shrimp, Tiger shrimp, Bumblebee shrimp, and filter-feeders; planarians and hydras die within 24–48 hours (in heavily polluted and quite large aquariums, a massive water change and repeated application after 48 hours is sometimes recommended).
Fish, plants, and valuable nitrifying bacteria do not react to Fenbendazole at “therapeutic doses”. Afterwards, be sure to perform a 50% water change to remove planarian corpses and toxins released by the dying worms. Repeat the procedure a week later (to destroy worms that hatched from eggs during this period), and after that, your aquarium should ideally become free of planarians. Special water cleanup measures using activated carbon after “treatment” are not required — regular water changes (slightly more intensive if desired). But be careful, Flubenol kills many species of mollusks, and besides, a disruption of the biological balance in the aquarium is possible after the therapy.
Also, hydras are readily eaten by some fish, such as Macropods, young blue (marble) gouramis, and loricariid catfish.
Genchem No-Planaria. An effective remedy for eliminating planarians in an aquarium. Instructions for use: Dose calculation for 50 l: First day — 1 measuring spoon. Second day — 1/2 measuring spoon. Third day — 1/4 measuring spoon. Thus, we get 72 hours. Within 72 hours, you will notice a significant decrease in planarians. If there are too many parasites, it is recommended not to decrease the dose for the following days. Planarians are dangerous to shrimp! Planarians crawl under the dorsal shield of crustaceans and further into the gills in search of food, causing shrimp to die from suffocation. The favorite delicacy of planarians is shrimp roe. If planarians have proliferated in your aquarium, you will notice a sharp mortality rate in aquarium shrimp.
With prolonged use, it kills nematodes and can decimate snail populations. Prolonged use refers to, for example, constantly adding the product every 2 weeks to control planarians. It is also important to note that after the 3-day course, it is necessary to siphon the substrate to clean it of parasite remnants and to change the water (so that snails do not get sick). The main active ingredient is Areca palm seed extract rather than chemical elements, meaning it is a natural material.
Shrimp foods – Mosura, Shirakura, Borneo wild, Dennerle.
Fungal diseases, Bacterial, Viral infections in shrimp. 
Latest updates and additions made on August 15, 2012.
