How to Get Rid of Hydra in Shrimp Tank?

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Setting up a thriving tank is generally easy, provided you follow specific installation guidelines. The real challenge, however, comes with the maintenance process.

The goal is to preserve the system’s health, stability, and sustainability over years to come. This means that you need to learn how to identify threats and combat and prevent them effectively to keep your aquarium healthy and safe for all inhabitants.

Today, we will discuss a scary but rather unaddressed threat that many aquarists will face at some point. We’re talking about the notorious hydra, the killer jellyfish-like entity prowling most aquatic environments.

What is a Hydra?

This creature’s name comes from the mythical Hydra, the monstrous offspring of Typhon (the son of Gaea and Tartarus) and Echidna, a half-woman, half-serpent monster.

Hydra itself was an abomination that lurked in the marshes of Lerna, which earned it the name of Hydra of Lerna.

The creature had 9 regenerative heads, which made it both fearsome and almost impossible to kill. Removing one of its heads would cause 2 to grow in its place.

It was Hercules who eventually disposed of the monster as part of its 12 Labors by cutting the creature’s heads one by one and burning the headless necks. This prevented the monster from regenerating.

So, what does this Greek mythology lesson have to do with our case today? Apparently, quite a lot. Our aquatic hydra shares many of its physical properties with that of the mythical being we’ve just discussed.

The animal ranks as a polyp which means it is related to jellyfish and corals.

It is small, up to 1 inch in length, although most are typically even smaller. Its body consists of a muscular, sticky foot that the animal uses to latch onto various surfaces.

The head consists of several tentacles armed with cnidoblasts which poison and paralyze the prey.

Fortunately, these animals aren’t a real danger to most larger tank inhabitants. They cannot kill or eat your adult fish unless we’re talking about really small specimens.

That being said, hydras are capable of consuming fish fry during their first days of life when they are especially vulnerable.

This is a rather fascinating animal, given that it possesses no brain, circulatory system, or musculature. Despite that, it is quite an effective killer, capable of spreading through its environment fast.

How do Hydra Reproduce?

The hydra’s reproductive system and behavior are among the most bizarre things about the animal. That’s because hydras reproduce similar to plants.

The reproductive process is asexual and is called budding. Witnessing it unfold in real-time is something to behold.

In short, the hydra will display a small swelling at the base of its foot. That’s the gastric area which will now give birth to another hydra. The swelling grows quite fast, depending on environmental conditions and nutrient intake.

Shortly, that bump will become a smaller hydra with its own tentacles, sharing part of its body with its parent.

The newborn hydra will detach shortly and become independent. This budding process takes place once every 2-3 days, with one hydra producing another hydra each time.

This can cause the animal to infest an entire aquatic environment extremely fast. That’s because each hydra produces another hydra every couple of days.

So, their number doubles every 2-3 days. Your aquarium can get overwhelmed fast.

But is this animal dangerous for your shrimp aquarium, and why?

Why are Hydras Dangerous to Shrimp?

Hydras are extremely effective predators, capable of killing and consuming a variety of prey. These carnivorous polyps don’t move much, fortunately, as they operate as ambush predators.

They stand still and wait for the prey to come near them, which they will identify via their cnidocytes. These are the stinging cells covering their tentacles and delivering the neurotoxin used to immobilize the prey.

As it turns out, these cells are light-sensitive and can detect specific proteins present in the bodies of potential prey. Including shrimp.

This means that the presence of shrimp, daphnia, or other smaller creatures in the hydra’s vicinity will cause the tentacles to react instinctively and move towards the victim.

This astounding evolutionary feature has allowed polyps like hydra to survive for over 600 million years.

Fortunately, hydras are too small to threaten your adult shrimp, so they will go for the young. Shrimp fry are vulnerable to hydras until they reach 1-month of age, which is plenty of time for hydras to kill your entire shrimp population.

If the food is sufficient, your hydras will multiply fast and kill every shrimp fry, no matter how many there are.

As you can see, hydras are quite the problem in both shrimp and fish tanks. After all, they are equally effective at hunting and killing fish fry too.

5 Shrimp-Safe Methods to Get Rid of Hydra in Fish Tank

If you want to get rid of hydra in a shrimp tank, you can manually remove them, use hydrogen peroxide, Seachem Excel, or you can use a chemical treatment such as No-Planaria powder. Small fish can also be used in a shrimp tank because these will eat the hydras.

Now, let’s see which is the most effective way for you to get rid of hydra:

1. Manual Removal

This is quite simple and straightforward, but only in theory. The idea is to use a syringe to suck in the hydra since the animal is too small to pick it up any other way.

The syringe will provide powerful-enough suction to displace the hydra from its environment in one piece. If the hydra breaks, the remaining parts can then grow to become new, independent hydras themselves, so caution is advised.

I rate this method as decent but not preferable to others. While you may be able to remove quite a handful of hydras, the real problem is not what you see but what you can’t see.

For every hydra you’re picking off, there are dozens or potentially hundreds of them lurking in areas where you can’t see them.

These animals are quite effective at rendering themselves invisible. On the one hand, they are nearly transparent, so spotting them in a lush aquatic setup with various plants, fish, and light refractions can be extremely difficult.

Then you have the fact that hydras often curl themselves into a ball when threatened or stressed. This will make them look like grains of sand or harmless matter floating around.

Manually removing hydras is useful for eliminating the more easily accessible specimens, but don’t use this method as your primary means of hydra control.

2. Hydrogen Peroxide

Hydrogen peroxide is useful for dealing with hydra and algae, but don’t expect any miracles.

The process is quite simple:

  • Turn off the filter to prevent the filtration system from removing the hydrogen peroxide immediately
  • Add approximately 1.5 ml of hydrogen peroxide per 1 gallon of water
  • Allow the solution to stew for approximately 1 hour
  • Restart the filtration system

This is generally enough to eliminate most of the hydras and clean the algae tank. Unfortunately, this method doesn’t have a 100% success rate.

Many hydras will escape with their lives, especially those buried in the substrate or taking cover under plants or other decorations. In their case, the solution may not affect or even reach them.

After all, this is a 600-million-year-old organism capable of adapting to even the most severe conditions. In short, hydrogen peroxide is only useful as a control method, allowing you to prevent hydras from spreading.

But it will not eliminate the aquatic parasite entirely.

3. Seachem Excel

Many people use Seachem Excel to address their hydra problems. This is pretty much an alternative source of carbon dioxide, which many aquarists use to replace CO2 injections. It is also popular as an algaecide since algae cannot survive in environments with certain CO2 values.

The same product can be used to address hydra infestations, but it’s not really as effective as people think. Seachem Excel is mostly effective when undiluted or in high-enough concentrations to kill the hydras on the spot.

Unfortunately, you can’t use too much of it in your shrimp or fish tank.

The amount you can use is typically ineffective at addressing your hydra problem. I only placed this method on the list because there are people using it.

But I wouldn’t recommend it as effective or reliable.

4. No-Planaria

No-Planaria is a hydra-specific product designed specifically to be used in shrimp and planted fish tanks. I would say that this is the most effective method of eradicating the hydra population without hurting your shrimp and fish in the process.

The method itself is easy to apply since you only need to follow the product’s instructions for optimal results. Just be careful about using No-Planaria if you have snails.

Some snail species are more sensitive to the product. To prevent any problems, you should relocate the snails to a temporary home until the treatment is complete.

I recommend this one if you’re interested in a No-Planaria treatment. The product is shrimp and fish-safe, and it doesn’t affect live plants.

Results may differ, as the product may take more time to deliver based on your tank’s size and infestation magnitude.

5. Adding Small Fish

This is a great option in case you don’t want or can’t use chemical treatments. Adding small fish like micro-rasbora (smaller than 1 inch) will allow you to create natural food competition for hydras.

Both hydras and micro fish consume similar foods, as they feed on the microorganisms floating in the tank water.

The difference is that hydras are passive hunters, while fish are active hunters. These fish don’t wait for the food to come to them; they will actively search for it.

These will cause them to outpace the hydras in terms of eating, effectively causing the resilient parasite to starve. 

In some cases, these fish can even eat hydras directly, provided they are hungry enough.

However, keep in mind that this is more of a control method than an elimination one. Hydras will continue to exist in your tank, but only in small numbers because the food sources will be so greatly diminished.

But these are resilient organisms, so food competition won’t really eradicate them.

Overall, I say that the most reliable hydra treatments are chemical in nature. No-Planaria is the best choice, as far as I can tell, but feel free to consult with a vet.

The expert may have better insight and assist you along the way for better and faster results.

How do Hydras Get into a Shrimp Tank?

Hydras will get into your tank the same way snails do – via hitchhiking. In other words, hydras move from one environment to the next via plants, rocks, or infected water decorations which the animal clings on.

If you think that this is unlikely to happen to you, consider the following:

  • Hydras can live several days out of water
  • Hydras can survive several weeks without food, provided they have sufficient lighting
  • Hydras are in a continual state of biological regeneration, which means they don’t age; theoretically, they have unlimited lives

They are also very difficult to spot since hydras curl into tiny balls when stressed, as is the case with them being kept out of water.

So, it’s quite easy for them to reach your tank via infected plants or even fish, as hydras sometimes attach to them.

That being said, infected plants remain the main transportation method. To prevent a hydra infestation, consider the following:

  • Treat and disinfect plants before use – Several disinfection methods are available, including bleach, potassium permanganate, hydrogen peroxide, or aluminum sulphate. The sterilization process itself usually lasts between 5 minutes and 2-3 hours, depending on which substance you’re using. Check my articles on the topic to learn how to perform each sterilization method safely and effectively.
  • Clean rocks – Rocks are even easier to clean since they’re less sensitive than plants. Scrub them to remove visible dirt, and then simply boil them. The boiling process will eliminate any pathogens, both macro and microscopic, that may be inhabiting the piece. Just remember to cool off the stone before immersing it in the tank. Stones retain heat quite well, so they might remain hot longer than you expect.
  • Quarantine fish – Any new fish should undergo a 2-week quarantine period to ensure it doesn’t have any parasites, infections, or bacteria that they may carry to the main tank. It’s not uncommon for hydras to come with the water bag or jar you’re getting your fish in, so be wary of that. Quarantining the new fish for a couple of weeks allows you to detect any organisms that may pose a threat to the general fish or shrimp population. You should do the same for newly acquired shrimp as well.

How to Prevent Hydra Outbreak in Shrimp Tank?

So, you have finally removed all of the hydras from your tank. Unfortunately, this isn’t a time to let your guard down.

A new infestation may occur at any moment if you do. To prevent that, consider the following:

  • Sterilizing and quarantining any piece of decoration or equipment you plan on adding to the tank work 
  • Identifying the presence of hydras in time to take early measures
  • Add natural predators like mollies, paradise fish, blue gouramis, or even some snail species like pond snails and asolene spixi

In this sense, the latter is the most environmentally safe and effective method. Just ensure that those predators won’t always prey on your shrimp and shrimp fry, which they might.

If you can’t rely on them for that reason, consider the addition of micro-fish like rasboras, who are unlikely to target your shrimp. They will consume the hydras’ food, causing them to starve and die.

Will Aquarium Salt Kill Hydra?

Iodine-free table salt is known to kill hydras. A concentration of 2 mg per 1 liter of water should do the trick, although not always.

These organisms are quite resilient, so many of them may overcome adverse odds. It’s not uncommon for aquarists to report a hydra bloom after salt treatment.

Not to mention, shrimp and fish are also sensitive to salt in high-enough concentrations, so be careful about it.


Hydras are amazing creatures that won’t impact your aquarium life too much. It’s not necessarily the end of your aquatic world if you spot one or several in your shrimp tank.

You just have to remember that hydras are quite effective predators, and they will eat your shrimp fry and spread fast under ideal conditions.

Fortunately, you now have the means to counter them effectively should they even become a problem you can no longer ignore.

Author Image Fabian
I’m Fabian, aquarium fish breeder and founder of this website. I’ve been keeping fish, since I was a kid. On this blog, I share a lot of information about the aquarium hobby and various fish species that I like. Please leave a comment if you have any question.
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