my female mollie

Question
My Dalmation molly looks like it keeps getting rounder everyday. Is it the amount of food i'm feeding it? Or is it pregnant? My Molly is also in the same tank as a goldfish, a Black Male Molly, and an Algae eater. Is it bad to put those type of fish together?

Thank you for your time!

Answer
Hello Sarah,
To answer your first question, it could be quite possible the fish is being overfed. You may want to skip a day or two of feeding and see if the swelling goes down. If not, your fish may either be pregnant - which  you can tell by the shape of their belly - when they're pregnant they tend to take on a more "boxy" look; or, it may have dropsy - which is often times fatal. Please be sure to look into the symptoms so you don't misdiagnose or even worse mistreat your fish. You may need to take a picture of the fish to help have it properly diagnosed.
Secondly, technically that set-up would be fine if it weren't for the goldfish. Goldfish - and plecos (your "algae eater") grow rather large. Also, your goldfish is a temperate fish, while your other fish are all tropical. Meaning they prefer and flourish in different temperatures of water. Please consider buying a new tank for your goldfish soon - 20 gallons or larger.
Hope this has helped, thank you for your question!