Do you use any tools to diagnose diseases?

I mostly just search online, or ask on communities like this what people think it may be. As far as tracking medicine doses, and lengths, I tend to just use a notepad to write everything down.

Although an app would be a sweet deal, 99.99% of them are paid and come with other junk attached.

Usually I research online as well.

Now everything that helps in diagnosis is available on the internet , you need to have good observation to identify if something feels off with your fish.