So I know goldfish poop a lot, but . . .

[Epiphanaea]

. . . is it normal for a fish to be pooping literally constantly?  I never see this fish without a string of poop.  She’s in a planted tank with lots of algae so she’s grazing constantly, but she’s not overweight, if anything I think she’s a little on the skinny side.  Her tankmate is a round little creature and poops what seems like a normal amount - non-constant, anyway.

Does she need deworming or something, or does she just have a speedy metabolism?

[Fish Folk]

Is the poop normally brown and average size? With worms, you'll usually notice a change in color to the fecal matter. IF the fish has found a constant source of food growing in the tank, it is possible that ... a lot is going in, and a lot is coming out. Keep the tank water-changed, and ensure that what you feed is fresh and nutritionally well-rounded. 

[Epiphanaea]

It’s usually green - sometimes beige after I’ve fed mysis shrimp.  She’s only about 2 1/2” and half of that is tail, so she’s definitely still growing, and has grown about a half-inch since I got her (about two weeks ago).  She’s nowhere near as round as her tankmate, but maybe she’s just growing fast?  

[thegoldiehook]

If she is eating constantly its good she is pooping constantly. I'm sure the algae is supplying her with lots of fiber so maybe adding more protein to her diet will help her put on weight. Goldfish do not have stomachs to store food like we do. It's like one long tube. 

Keep an eye out for constipation. If you see she is still grazing and eating and not pooping, that's when you may have an issue. But I wouldn't be too concern because of all the fiber she is getting.