No idea if Flubendazole treats external protozoan parasites. Praziquantel is meant to treat white spot and could potentially treat other types of external protozoa (velvet, Costia, Chilodonella, Trichodina). More research into this is needed. However, salt does treat the latter 3 parasites.
If you want to have anything on hand, have rock salt (aquarium salt), deworming medication if you plan on getting in a few fish, and a bottle of dechlorinator.
If fish act unwell or start to show signs of an illness, doing big (75%) water changes and gravel clean the substrate every day can dilute any pathogens in the water and slow the spread of the disease. And if the issue is caused by poor water quality (and it often does), the water changes will help with that too.
My go to for most diseases is clean water and salt.
As for white spot and velvet, warm water (30C/ 86F) for a couple of weeks and if it's not responding then get Malachite Green (aka Victoria Green) or copper. There are other ways to treat white spot and velvet, see post 16 in the link on this forum "What is ICH"
Copper is toxic to invertebrates (shrimp, snails, etc).
Malachite Green is a carcinogen (causes cancer).
Take your pick, they both work but both have drawbacks.
WHAT IS ICH? Ich or Whitespot is a parasitic protozoan that infects fresh, brackish and saltwater fishes. It is identified by small white spots that appear on the fish's body & fins. There are several stages to this parasite's lifecycle and it must be noted that the parasite can only be killed...
www.fishforums.net
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SALT
Using Salt to Treat Fish Health Issues.
For some fish diseases you can use salt (sodium chloride) to treat the ailment rather than using a chemical based medication. Salt is relatively safe and is regularly used in the aquaculture industry to treat food fish for diseases. Salt has been successfully used to treat minor fungal and bacterial infections, as well as a number of external protozoan infections. Salt alone will not treat whitespot (Ichthyophthirius) or Velvet (Oodinium) but will treat most other types of external protozoan infections in freshwater fishes. Salt can treat early stages of hole in the head disease caused by Hexamita but it needs to be done in conjunction with cleaning up the tank. Salt can also be used to treat anchor worm (Lernaea), fish lice (Argulus), gill flukes (Dactylogyrus), skin flukes (Gyrodactylus), Epistylis, Microsporidian and Spironucleus infections.
You can add rock salt (often sold as aquarium salt), swimming pool salt, or any non iodised salt (sodium chloride) to the aquarium at the dose rate of 1 heaped tablespoon per 20 litres (5 gallons) of water. If there is no improvement after 48 hours you can double that dose rate so there is 2 heaped tablespoons of salt per 20 litres.
If you only have livebearers (guppies, platies, swordtails, mollies), goldfish or rainbowfish in the tank you can double that dose rate, so you would add 2 heaped tablespoons per 20 litres and if there is no improvement after 48 hours, then increase it so there is a total of 4 heaped tablespoons of salt per 20 litres.
Keep the salt level like this for at least 2 weeks but no longer than 4 weeks otherwise kidney damage can occur. Kidney damage is more likely to occur in fish from soft water (tetras, Corydoras, angelfish, Bettas & gouramis, loaches) that are exposed to high levels of salt for an extended period of time, and is not an issue with livebearers, rainbowfish or other salt tolerant species.
The salt will not affect the beneficial filter bacteria but the higher dose rate (4 heaped tablespoons per 20 litres) will affect some plants and some snails. The lower dose rate (1-2 heaped tablespoons per 20 litres) will not affect fish, plants, shrimp or snails.
After you use salt and the fish have recovered, you do a 10% water change each day for a week using only fresh water that has been dechlorinated. Then do a 20% water change each day for a week. Then you can do bigger water changes after that. This dilutes the salt out of the tank slowly so it doesn't harm the fish.
If you do water changes while using salt, you need to treat the new water with salt before adding it to the tank. This will keep the salt level stable in the tank and minimise stress on the fish.
When you first add salt, add the salt to a small bucket of tank water and dissolve the salt. Then slowly pour the salt water into the tank near the filter outlet. Add the salt over a couple of minutes.
