Praziquantel (dewormer)

What It Treats – Flukes (Monogeneans), Black Ich (Turbellarians), and intestinal worms.

How To Treat – There are a few aquarium products which contain praziquantel: Prazipro, API General Cure and Thomas Labs Fish Tapes. Follow the dosing instructions for whatever product you are using. If using straight powder praziquantel powder, dose @ 2.5 mg/L (or 9.5 mg/gal). Powder praziquantel is not easily water soluable and it often helps to mix your dose in a small amount of ethyl alcohol or even common vodka before dosing your tank.

With prazi dose once, wait about a week, do a 20-25% water change and then repeat dosage. (Or use this treatment calendar to determine when is the best time to add the second dose.) The reason for the second dose is to eradicate the “next generation” of worms before they can lay eggs of their own. Because while Prazi does kill worms, it doesn’t eliminate any eggs they might leave behind.

If you are treating a known prazi sensitive species (e.g. wrasse), you can run carbon or perform a water change 24 hours after dosing in order to limit exposure time. While praziquantel does remain active in the water column for up to 72 hours, only 24 hours are needed for it to eradicate external worms. Don’t forget to still do the second round though!

Prazipro is generally considered reef safe, although it may kill any tube worms/feathers dusters you have. It may also eradicate bristle worms. If you have mass quantities of these, the resulting die-off can lead to an ammonia spike. After treatment is done, activated carbon may be used to remove any residuals (if you need to use a different medication next). This is important because the Oxybispropanol (solubilizing agent) Prazipro contains will sometimes cause a bacterial bloom (cloudy water) when mixed with other meds. If using a protein skimmer post-treatment, be advised that it will “over skim” for at least a week or so.

API General Cure contains both praziquantel and metronidazole, and is an effective substitute for using Prazipro. (Just don’t follow the 48 hour repeat dosage instructions; Redose 5-7 days later instead.) But where General Cure really shines is when soaked in food to treat both intestinal worms and internal parasites (flagellates). Both maladies share one classic symptom: White stringy feces. You can also food soak Thomas Labs Fish Tapes or just straight praziquantel powder; but be aware that prazi only treats intestinal worms. (You would need to food soak metronidazole for internal flagellates.) I recommend feeding the medicated food daily for 2-3 weeks, or until symptoms are no longer present. My recipe for food soaking prazi (and metro) can be found below:

Using a shot glass:
1 scoop (~ 1/8 teaspoon) of medication
1 scoop Seachem Focus (this makes it reef safe)
1 tbsp food (preferably pellets or frozen food)
A pinch of Epsom salt to help expel dead worms/parasites
A few drops of saltwater or fish vitamins
Stir until a medicated food slurry has been achieved
Feed after soaking for 30 mins
Refrigerate or freeze any leftovers for future use

Pros – Reef safe, effective dewormer that is relatively gentle on most fish.

Cons/Side Effects – Mild appetite suppression, moderate oxygen depletion, wrasses are sensitive to overdosing. Prazi resistant worms (both external and internal) do exist, so sometimes an alternative treatment must be used instead. This includes hyposalinity or formalin (to treat external worms), and food soaking Fenbendazole to deal with prazi resistant intestinal worms.