How to Treat Parasites In Aquarium Fish

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How to Treat Parasites in Aquarium Fish

When you buy an aquarium fish, did you know that it has traveled from a fish farm to a wholesaler to a pet store before it got to you? This means that your fish could have acquired an internal or external parasite. Wild-caught fish can be susceptible to multiple parasites. Aquarium fish are often not kept in the store for long enough to check for parasitic diseases. If your fish has visible parasites on its body, a swollen abdomen, skinny disease, hole-in-the-head, or strange-looking, discolored poop, you may need to treat it with one of the following antiparasitic medications.


1. Ich-X

Hikari are well-known for making high-quality fish meals. However, they also produce great fish medications under the Pond Solutions and Aquarium Solutions product lines. After testing dozens ich medicines in the United States we found Ich-X to be the most effective for treating ich, white spot disease, other external protozoan parasites, and mild fungal infections. In fact, we use Ich-X to proactively treat all fish that enter our fish store before they get sold to customers. Its active ingredients are formaldehyde and malachite green chloride, and it is safe for scaleless fish, invertebrates, and live plants.

If your fish looks like it’s covered in little, white grains of salt, it could be ich and needs to be treated immediately. You should always keep first aid medication like Ich-X handy.

There are two types of Ich-X: Aquarium Solutions Ich-X for home aquariums and Pond Solutions Ich-X for ponds and larger tanks that contain 50 gallons or more. These are the steps to use Aquarium Solutions IchX

1. Perform a water change. Remove any chemical filtration (like activated carbon or Purigen) and UV sterilizers. 2. Dose the aquarium with 1 teaspoon (5 ml) of Ich-X per 10 gallons of water. 3. Each 24 hours, change one third of the tank water. Then, repeat the dose. 4. Keep your treatment going for at least three more days after you have seen any symptoms of the disease.

Pond Solutions IchX is more powerful than Aquarium Solutions IchX. Follow the same directions, but use a dose of 1 teaspoon (5 ml), per 50 gallons. You can read the full article to learn more about how to treat ich.

2. ParaCleanse

Fritz ParaCleanse, another proven medication that we use to preventively treat any new fish entering our retail store is safe and can be used safely in conjunction with IchX. It is used to treat internal parasites as well as some external parasites like:

– Tapeworms (e.g., skinny or wasting disease) – Gill and skin flukes (e.g., Gyrodactylus species) – Hole-in-the-head (HITH) disease (e.g., Hexamita and Spironucleus species)

ParaCleanse has praziquantel for worms and flukes. It also contains metronidazole for certain bacteria and protozoans. It is safe for fish, fish fry (scaleless), shrimp, snails, and aquarium plants. If you suspect your fish has one of these parasites, follow the manufacturer’s directions and do not treat with half doses (or else the medicine may not be effective).

1. Clean the aquarium, and get rid of any UV sterilizers and chemical filtration. 2. On Day 1, dose 1 packet of ParaCleanse per 10 gallons of water. 3. Dosage 1 packet ParaCleanse to 10 gallons of drinking water per day. 4. On Day 5, perform a 25% water change on the aquarium. 5. To give your fish the best chance of recovering and gaining weight, wait 2 weeks before you administer any other medication. To help them pass the dead worms, feed foods with fiber and roughage, such as spirulina brine shrimp, daphnia, algae wafers, and Repashy Soilent Green. 6. Follow Steps 1-4 for a 5-day repeat treatment after two weeks. (Eggs are not affected by the medicine, so we have to wait for the new worms to hatch out. It takes 2 weeks for internal parasites to be completely eliminated in stores before fish can be sold. 7. [Optional] Doing the 5-day treatment twice gets rid of the majority of parasites. You can make sure that your fish are healthy by waiting 2 weeks before repeating Steps 1 through 4.

Tapeworm eggs are not affected with most medications so we need to wait until new worms hatch before treating them. That is why we recommend redosing after 2 weeks once they have hatched.

ParaCleanse does not cause any harm to fish, and multiple treatments can be used. It can be expensive so make sure to put your fish in a smaller tank.

Should the fish be medicated with food or water? It can be difficult to manage medicated fish food. Sick fish often won’t eat very much (or at all) because they don’t feel well. It can also be difficult to keep track of how much medication each fish is taking. This could lead to fish consuming too many medications while others are eating too little. If you are only treating one fish that is still eating well, then medicated food might be a viable option. For multiple animals we recommend medication that dissolves in the water. We can then treat each animal with the same medication.

How does this treatment plan work with the quarantine med trio? If you have proactively treated your new fish with a 7-day soak using ParaCleanse, Ich-X, and Maracyn, then follow the above instructions starting with Step 5.

3. PraziPro

PraziPro contains a higher level of praziquantel. We recommend PraziPro when ParaCleanse doesn’t work or if there are problems with shrimp parasites such as Vorticella or Scutalleria japonica.

PraziPro works in a similar way to ParaCleanse. It is safe for fish and invertebrates as well as plants and beneficial bacteria. PraziPro is used primarily to treat flatworms, tapeworms, flukes and turbellarians. These are the steps to use PraziPro:

1. Clean the aquarium, and get rid of any UV sterilizers and chemical filtration. 2. Shake the bottle well and dose 1 teaspoon (5 ml) of PraziPro per 20 gallons of water. 3. Allow the medication to rest for 7 days. Repeat the dosage as necessary, but no more than once every 3 days.

Many parasites are found in wild-caught fish and may need three treatments to completely deworm them.

PraziPro has been used in our personal tanks to deworm our puffers. We first treat ParaCleanse 5 days, then wait 2 weeks. We then do another 5-day ParaCleanse treatment, and then we wait a full month. The final step is the PraziPro 7-day treatment.

4. CyroPro

Pond Solutions CyroPro was specifically formulated to deal with external parasites like anchor worms and fish lice (e.g. Argulus) Cyromazine is an active ingredient that prevents parasitic insects from molting their exoskeletons. It is safe for plants and fish. However, you should consider removing any shrimp, crayfish or other crustaceans prior to treatment.

1. Make sure to water change the aquarium and pond. Also, get rid of all chemical filtration or UV sterilizers. 2. Give the CyroPro a good shake and 1 teaspoon (5 ml), per 50 gallons. 3. Repeat the treatment seven days a week for at least 21 days. If you are absent from a treatment day, restart the treatment.

External parasites such as fish lice (seen in the photo above) and anchorworms can be seen to the naked eye. They are commonly found on pond fish, like goldfish or koi.

The water changes that occur before CyroPro are used to restore dissolved oxygen, remove excess nutrients, and decrease the population of water-borne parasites.

5. Expel-P

Fritz Expel-P is a fast-acting dewormer used to specifically treat parasites such as planaria, roundworms and nematodes (such as camallanus red worms), nodular worms, and hookworms. Infected fish may exhibit signs such as anemia, a swollen stomach, red worms leaking into the anus, rapid breathing, or loss of appetite.

The active ingredient is levamisole hydrochloride (HCl), which causes paralysis and death of the worms, but it will not harm your biological filtration, aquarium plants, invertebrates, or healthy fish.

Fritz ParaCleanse recommends multiple treatments to ensure all eggs hatch. Follow the manufacturer’s instructions and recommended dosage:

1. Clean the aquarium, and get rid of any UV sterilizers and chemical filtration. 2. One packet of ExpelP for every 10 gallons of water. 3. Do a 25% water exchange after 24 hours. Use an aquarium siphon to vacuum the substrate to get rid of any paralyzed or injured worms. 4. After 1 week, repeat the treatment to get rid of any new worms that hatched out. 5. Continue the weekly treatments as needed until the worms have disappeared or the fish are regaining weight again.

Bonus: Aquarium Salt

Aquarium salt can be used to treat external parasites if you don’t have access to them. However, it is not as effective as internal parasites. The salt works by dehydrating the parasites to death before the fish (which have more mass and stored water) are affected. For complete instructions, see our full article on how to treat sick fish with salt.