Stardew Valley has plenty of fish in the sea. And lakes. And ponds. And rivers. Look, the point is there’s a ton for you to catch. One such fish (that is also necessary for a Community Center bundle) is the Ghostfish.
The Ghostfish is a bit rare, though, so you won’t have that easy of a time catching one. The easiest way to get a hold of one is by heading to the mines. Make your way to level 20. Once there, you’ll notice that there’s an underground lake. Start fishing. You’ll get some algae here and there, but your primary bites will be from ghostfish as they’re very abundant there. Upgrade your rod to have an easier time catching them, too.
There you have it, a steady supply of ghostfish is at the palm of your hand! You might also get lucky and be able to buy one from the Travelling Cart, but this is your best bet. If you need more help with Stardew Valley, check out our wiki!