Yes. You don’t have to use fish fertilizer, any nitrogen fertilizer should do the trick. I find fish fertilizer helps build good soil over time though. Also, it won’t burn your plants, so it’s a bit more user friendly than chemical fertilizer.
Usually it comes in a plastic jug and you have to dilute it quite a bit before using. Just follow the instructions on the package.
Once the pumpkins start growing it’s gonna get pretty potassium hungry. You can switch over to a seaweed fertilizer to get nice big pumpkins. But it needs lots of leaves and plenty of sun first, to fix the necessary carbon.
Aren’t they all?