When most people think of parasites affecting their pets, they imagine heartworms in dogs or roundworms in cats. However, parasites can also have an adverse effect on aquariums, causing health problems among fish and creating an unstable underwater habitat. But what are some common parasites that affect aquariums—and more importantly, how can new fish owners avoid getting them?
Here’s everything you need to know about freshwater and saltwater parasites, including how to recognize signs of an infestation and steps to remedy it.
1. Hydra: Dangers to Fry and Small Fish
Hydras are among the most dangerous parasites that can affect freshwater aquariums. These organisms are soft-bodied polyps that, much like jellyfish, have stinging properties. They use this unique adaptation to immobilize and capture prey, which can include fry, small adult fish, and small crabs. If left unmanaged, you may have fish and other underwater critters start going missing!
Hydra can be introduced to freshwater aquariums when adding new plants to the tank. Hydra can “hitchhike” on these plants and then reproduce quickly once in the water. They don’t need a male or female hydra to mate, as these organisms produce asexually. While they don’t have a brain or lungs, they can still infest an aquarium and prove very difficult to remove.
Thankfully, you have options. Upon noticing these small, tubular creatures in your fish tank, you could add fish to your aquarium that naturally feed on hydra, such as mollies and paradise fish. You could also attempt to eradicate the parasite with a deep cleaning or by heating up the water (with the fish removed!).
2. Ciliated Protists Are Common External Parasites
Merck Veterinary Manual notes that ciliated protists are the most common external parasites in fish. Ichthyophthirius multifiliis is the most commonly known, and it is sometimes referred to as “ich” or “white spot disease”. This organism can affect all freshwater fish, and once a fish is infested, it may show signs of:
- Lethargy
- Clamped fins
- Discoloration, such as white spots
The fish may also have a small wound where the parasite burrowed into its skin. Formalin or copper are both methods of treating these parasites and the conditions they can cause. If ciliated protists aren’t spotted quickly, they can spread from fish to fish, jeopardizing their health and proving difficult to address.
3. Planaria Can Eat Vulnerable Shrimp
If you have a small fishtank or vivarium, you may keep ghost shrimp. These translucent creatures are excellent scavengers, often eating uneaten, decaying food. However, they can be threatened by planaria, flatworms with arrow-shaped heads. Planaria are most likely to eat baby shrimp or those that have recently molted (and are therefore more vulnerable). The good news is that your fish are likely safe.
Many aquarists will spot planaria moving under the substrate against the tank’s glass. You can prevent these parasitic flatworms by regularly cleaning your aquarium and ensuring that you don’t overfeed your fish. You may also choose to add corydoras or loaches to your fish tank, as they will happily eat any worms they see. Avoid using chemicals; these agents can hurt marine life if used excessively or improperly.
4. Limpets Can Have Pros and Cons
Limpets are gastropods that can infest both saltwater and freshwater aquariums. Like planaria, these organisms are generally harmless and will not affect your fish’s health. Yet, they can become an eyesore if there are too many squiggling around your aquarium. Before you research how to exterminate them, there are some things to consider first. Limpets are scavengers and will eat uneaten food that has accumulated inside the tank. According to Buceplant, many aquarists don’t bother removing limpets and claim they help with aquarium maintenance. They even note that the limpet population will die down after sudden increases.
It can be difficult to remove limpets (particularly from freshwater aquariums) because little is known about their habits. Still, you can reduce these parasites in your tank by removing any algae buildup or manually removing them yourself. You can also add fish that naturally eat parasites, such as some bottom dwellers.
5. Water-based Insect Larvae Can Signify Poor Filtration
Every aquarium should have a water filtration system. These mechanisms work to provide aeration, remove debris, and maintain good water quality. If you have an outdoor aquarium, a proper filter is especially important to make sure that no unwelcome pests call your fish tank home.
Insects such as dragonflies and mosquitos lay their eggs in bodies of water, where they can hatch and start to mature. With a strong filter, the larvae will likely get sucked into the water column and be removed. Yet, if you see multiple swimmers in your tank, this could mean that you need a new filter. As a rule of thumb, you should have a filter that can cycle your aquarium’s water four times in an hour. So, if you have a 30-gallon tank, you need a 120-gallon-per-hour filter.
If you have a filter that’s the right strength, but you’re seeing mosquito or dragonfly larvae in your aquarium, this could mean that the system isn’t working, and you need a new one.
How to Prevent Parasites in Your Aquarium
Preventing parasites from affecting your fish or aquarium’s aesthetic is fairly straightforward. Some tips include:
- Regularly cleaning your fish tank. During this process, you should replace 25 percent of your fish tank’s water. You should also wipe down tank decorations and test the water quality.
- Quarantining new fish. If you’re adding a new fish to your aquarium, you should quarantine them for at least two weeks. This involves placing them in a back-up tank and monitoring for any signs of illness. That way, if you notice anything awry about your new fish, you can prevent them from spreading diseases to new tankmates.
- Inspect new plants. When adding plants to your aquarium, inspect them for snails, worms, and other organisms. That way, you can ensure that nobody hitches a ride!
