Remember the age old saying “if there’s one, there’s more”? Flatworms are no different. Marine hobbyists are eventually going to run into them, and it’s important to be prepared. While not all flatworms are bad, we’re going to go over what ones are and how to take care of them.
Flatworms belong to the phylum family Platyhelminthe, but are also known as tapeworms or flukes. While flatworms have a reputation for being invasive and destructive, subspecies of flatworms range from parastic to purely an eyesore. Luckily, taxonomists have researched this spectrum and have separated the over 20,000 members of the Platyhelminthe family into four main categories: Turbellaria, Trematoda, Monogenea, and Cestoda. While these four categories are helpful if you want to get real nerdy, aquarists have created their own sort of categorization tailored to what we most commonly see in marine aquariums.
Rust Brown Flatworms / Red Planaria
Convolutriloba retrogemma, otherwise known as the rust brown flatworm or red planaria, is the most common flatworm found in a hobbyist’s aquarium. You can identify the flatworm by its rust brown color, bright red dot on the lower half of its body, and its oval shape taping off into two tails. These flatworms love nutrient rich water and reproduce quickly, so quickly that they can cover a coral’s surface and block light from reaching them. Their favorite spot to roam is on the surface of corals with low water movement.
Acropora Eating Flatworms
Acropora Eating Flatworms (AEFW), or Amakusaplana Acroporae, is generally considered the most detrimental flatworm to reefers. These flatworms are white and oval shaped, typically found on Acropora coral. It is most commonly found on smaller polyped corals, such as the Staghorn and Tricolor species, until that source has been depleted. You may start to notice these flatworms when your Acropora begins to show signs of loss of tissue with golden brown eggs left on the remaining skeleton.
Flatworm Control
If you’re reading this blog, you’re most likely looking for a solution to a flatworm takeover. Depending on the severity of your flatworms, there are differing ways to combat them. It is extremely important to accurately diagnose how many flatworms are in your aquarium. When flatworms are killed, they release a toxin that spreads throughout the water and is fatal to your fish, coral, and bacteria. This toxin, a potent neurotoxin called tetrodotoxin (TTX), is the same toxin pufferfish releases in defense to a predator. Studies show that TTX is only found in small quantities maternally, suggesting that a diet containing organisms such as flatworms largely contributes to a predator’s toxin count. In addition to this toxin, a large amount of flatworms killed at once produces a toxic amount of ammonia. These two factors combined can eradicate your entire system. If your flatworm takeover is covering more than 25% of your aquarium, it may be best to restart the entire system. Even with a complete water change, you can not successfully remove enough dead flatworms to stop toxins from infiltrating your water.
How Flatworms Are Introduced into Aquariums
Fragmenting corals, or “fragging” corals, has become the new normal in the marine hobbyist community. Frag shows and trading and selling coral has promoted aquaculture and connections throughout the hobbyist community. However, coral transferred between aquariums introduces a higher risk of also transferring hitchhikers and parasites such as flatworms. This is why it is vital to dip, thoroughly inspect, and/or quarantine any new coral being introduced into your aquarium.
Natural vs Chemical Treatment
Marine hobbyists typically prefer biological treatment rather than chemical treatment. While biological treatment is natural and benefits the aquarium’s inhabitants, it also does not spike parameters. Chemical treatment does not allow you to have as much control, treating everything at once and introducing more risk. Fish who eat flatworms will hunt and digest them at a natural pace over time, allowing for your parameters to keep up and level out. Chemical treatment, depending on your execution of the treatment and flatworm population, will heavily spike parameters and require you to be very careful on caring for the aquarium post treatment.
Many fish are natural flatworm hunters. Wrasses are the best way to naturally eradicate your flatworm population. Six Line, Yellow Coris, Malanurus, Leopard, and occasionally Mandarin Gobies are the most active flatworm hunters. Blue or Springer Damsels are also adept at targeting flatworms. As a baseline, it is smart to keep one or more of these species in your aquarium as a precaution. Using natural remedies such as introducing a wrasse into your system is a great way to start controlling your flatworm population.
If natural methods are not successfully depleting your flatworm population, it may be beneficial to go the chemical route. This is where it is extremely important to take precautions and follow directions of treatment very carefully. The most common chemical treatment is Salifert’s Flatworm Exit™ or Blue Life’s Flatworm RX™. When using these treatments, keep your pumps on to ensure circulation to your entire system. However, turn off any skimmers, sterilizers, generators, mechanical filters, and remove any carbon to allow the medication to work. After following the treatment’s instructions, add carbon and turn back on all equipment to pull any remaining toxins and ammonia from the water. Depending on how your parameters read post treatment, determine how much of a water change to execute. Please refer back to the “Flatworm Control” portion of this blog to help you diagnose if you should use chemical treatment or not. If you are worried about side effects on coral and fish, but would still like to use a chemical treatment, place all fish and coral in quarantine while treating your aquarium. Make sure to dip or quarantine your coral prior to placing them in your new system.
Restarting Your Aquarium
If your aquarium has become completely overrun by flatworms, it is time to restart. Remove everything from the aquarium, including water, rock, sand, fish, and coral. Place your fish into a quarantine tank and dip all treatable coral before placing them in quarantine as well. Remove pumps and clean the entire tank using hot water. If hot water is not adeptly removing all substances, use equal parts vinegar and water. Citric acid can be used to clean equipment. Now you may start fresh. Make sure to add a wrasse as quality control!
We hope this blog has helped you understand what flatworms are and how to treat them! If you need help regarding flatworms, please reach out!
Sources:
https://www.sciencedirect.com/science/article/abs/pii/S0045653520304100#:~:text=The%20marine%20polyclad%20flatworm%20Planocera,the%20species%20has%20been%20unexplored.