garlic ,ginger ,tincture made of walnut (the green thigs wich covers the nuts till they are growing ).By parasites i assume you mean parasits living in human body .
Eat plenty of garlic, if you can. Garlic cleans the blood and actually gives it a weird taste, which mosquitoes don't like. Other than that, ginger is also good to have in a little satin bag, perhaps.
Citrus is also a good way to keep them away, especially lemon. They dislike it very much as it is too overpowering.
Other than that, there's no spell that can wipe out the entire insect population. Don't you think that is a bit harsh? I agree with one of the comments above. They are here for a purpose. Creatures like the butterfly are so beautiful.
If you don't want to use either of those, simply buy insect repellent and they won't bother you.
Perhaps I'm a little cold for saying this, but if there are parasites in your fish tank isn't it your fault that the fish died? You need to clean the tank, buy the special tank cleaners, and keep them healthy. I had a single guppy (fred the fish) for 3 years along with a snail (yurtle). Don't tease me on the names!
I don't know everything about fish, but I know guppies only live for 1-2 years so I must have done something right. Goldfish kill each other. So do other fish when you don't feed them enough. They will actually eat each other. Also some tank cleaning fish, if the tank is too clean will attack the fish. Some snails (I discovered the hard way) are asexual and will spawn babies that look a lot like parasites but eventually they grow tiny shells (very cute). I flushed a few batches of baby snails thinking they were parasites until my fish died of old age, then I left them alone and had a snail farm. Not exactly what I wanted, but oh well!
You ment ,parasites in fish thank !That will be the last thing which could have come in my mind .You need to be more specific in your threads ,that will save us a lot of confusion and time .I have no clue on any fish thank related topics and i doubt that the fish itself will like any garlic or ginger lol .Neither i assumed a fish tank related question will pop out in magical forum .
Revenge on parasites because they killed your fish? That's called the circle of life. Should have taken better care of your fish's environment. Other then that, I couldn't help but laugh for a minute or two at the revenge on the parasites comment.
To use magic on something that happens naturally seems a bit unreasonable, but to get rid of an infestation because it is affecting your health, with something as common as natural methods is a positive course of action. Natural ways include garlic intake, depending on the type of parasite of course.
