I can't cure any fish I bought a million bottles of medicine they still won't heal

Are you sure that you're buying the right medicine for the sickness that you're trying to cure? There are two fish diseases: ick (which looks like white specks on the fish's tail) and fungus (which looks like greenish-yellow globes attached to the fish's tail). You have to use the right one or the fish won't be cured. Sometimes it takes more than one bottle, but I've never seen it take more than two. Let me know if that doesn't help you.

OK

I have found that by putting the dropper directly on the affected fish, 50% of the time it is cured immediately. I have never had to go through more than 3 doses to cure a fish, rarely more than 2 by using this method. Has anyone else found this to be effective?

I am so addicted to this game...

Early in the game it is cheaper to flush the fish down the toilet than curing it ..... at 30$ per Ick treatment for a fish that sells for 7-15$ is madness

That's a decision that most people have to make at some point. It usually doesn't take the entire bottle to cure a fishie, so the actual cost is less than $30-40 to treat the disease. But in the beginning when cash is tight, most people trash a sick fish (unless it's an important part of your breeding program and is producing valuable offspring)! I've even been able to sell sick fish and not have to cure them or trash them.