How to Treat Parasites In Aquarium Fish

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 are especially prone to carrying parasites, if not multiple types at the same time. Most aquarium fish don’t stay in the store long enough for parasitic diseases to be checked. The following antiparasitic medications may be necessary to treat visible parasites, discolored poop, slimming, or skinny fish.


1. Ich-X

Hikari is well-known for their high-quality fish foods, but they also produce excellent fish medications under their Aquarium Solutions and Pond Solutions product lines. After testing dozens of ich medicines in the United States, we have determined that Ich-X is one of the most effective formulations for treating ich (or white spot disease), other external protozoan parasites, and mild fungal infections. Ich-X is actually used to prevent any fish from being sold to customers. It contains formaldehyde as well as malachite blue chloride. It is safe to use on scaleless fish, invertebrates and live plants.

If your fish appears to have a lot of white salt crystals, it may be ich. It’s important to have Ich-X and other first-aid medications on hand.

There are two types: Aquarium Solutions IchX for small aquariums, and Pond Solutions IchX for larger tanks with 50 gallons and more. To use Aquarium Solutions Ich-X, follow these steps:

1. Clean the aquarium and do a water change. Remove any chemical filtration (like activated carbon or Purigen) and UV sterilizers. 2. One teaspoon (5 ml), Ich-X for every 10 gallons water is recommended. 3. Change one-third of your tank water every 24 hours and then repeat the dosage. 4. Continue daily treatment for at least 3 days after you last see any signs of 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 can also be safely combined with Ich-X to preventively treat new fish in our retail shop. It can be used to treat both internal and external parasites such as:

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

ParaCleanse includes praziquantel, which is used to treat worms or flukes. Also, metronidazole is used to kill certain bacteria. It is safe to use on scaleless fish, fish fry and shrimp as well as snails, shrimp, and aquarium plant species. 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. ParaCleanse is administered once daily for 10 gallons. 3. Dose 1 packet of ParaCleanse for every 10 gallons water on Day 3. 4. Perform a 25% water change at the aquarium on Day 5. 5. Wait 2 weeks before administering any other medications so that your fish have a chance to recover and gain weight. 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. (The medicine doesn’t affect eggs, so we need to wait for the new larvae to hatch. This 2-week interval is why it’s hard for stores to completely get rid of internal parasites before fish are sold.) 7. [Optional] The majority of parasites can be eliminated by repeating the 5-day treatment once. For a second treatment, wait two weeks.

Tapeworms eggs do not react to most medications. We must wait until the new larvae hatch so that we can treat them. That is why we recommend redosing after 2 weeks once they have hatched.

ParaCleanse is not very harsh, so multiple treatments are generally safe for your fish. However, it can be a little expensive on the wallet, so try putting your fish in a smaller quarantine tank so that there is less water volume to dose.

Is it better to medicate the fish’s water or their food? Medicated fish food is a little tricky to manage. Because they are sick, sick fish will often not eat as much or as often as normal. Also, it can be hard to monitor how much medicated food each fish is getting, so some fish may be consuming too much medicine while others are consuming too little. Meditated food might be an option for treating one fish, if the fish is still eating well. If you are treating multiple animals, we recommend medications that dissolve in the water and treat the whole tank so that we can ensure every animal gets the right concentration.

What is the treatment plan for the Quarantine Med Trio? After you have given your fish a 7-day soak with ParaCleanse and Ich-X, follow these instructions, starting at Step 5.

3. PraziPro

PraziPro has a higher concentration of praziquantel, so we recommend using it when ParaCleanse isn’t quite strong enough or if we’re seeing a problem with certain shrimp parasites like Vorticella and 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 your aquarium and get rid all chemical filtration or UV sterilizers. 2. Shake the bottle well and dose 1 teaspoon (5 ml) of PraziPro per 20 gallons of water. 3. Let the medication sit for 7 days. Then, repeat the process as many times as you like.

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. First, we treat ParaCleanse for 5 days and then wait two weeks. We then do another 5-day ParaCleanse treatment, and then we wait a full month. As our final deworming step, we apply the PraziPro 7 day treatment.

4. CyroPro

Pond Solutions CyroPro has been specially designed to treat external parasites such as fish lice (e.g. Argulus species) or anchor worms, (e.g. Lernaea species). The active ingredient of cyromazine works by preventing parasitic insects and crustaceans 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. For at least 21 consecutive days, change the water and continue the treatment every 7-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 before each dose of CyroPro helps to refresh dissolved oxygen levels, remove excess nutrients, and reduce 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. Symptoms in infected fish can include an emaciated body, swollen abdomen, red worms leaking out of the fish’s anus, loss of appetite, or rapid breathing.

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.

Like Fritz ParaCleanse, multiple treatments are recommended to ensure that all the eggs have hatched and can be affected by the medication. Follow the instructions of your manufacturer and take the 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. You can repeat the treatment once more worms have hatched after one week. 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.