Q&A for How to Determine the Sex of a Fish

Look for a rounder, thicker body shape. Female goldfish tend to have a rounder, thicker body shape than males of the same age and species.

No, but you could check its anal fin. If it's long and skinny, the fish is male, if it's curvy, the fish is female.

Not necessarily. One of your fish is most likely younger than the other. Look up on the web what each gender looks like.

It is because the tilapia usually live in small tide pools similar to ponds.

Talk to your vet for advice.

It is almost impossible to tell Oscars apart by looking at them. The only way you can really tell is by seeing if it starts laying eggs, in which case it would be a female.

Simply from the coloration of their body, their size, the pelvic fins and dorsal fins––the male has pointed pelvic fins and large dorsal fin compared to the female. Use the tips in the article above to assist you fully.

Males tend to be shorter bodied with a slim build, while females tend to have longer and bulkier build. Although this alone is not an accurate way of sexing a snakehead because age, diet and care standards can all affect the growth and build of a fish.

With tetras being such a large family, it really depends on species. Smaller tetras like neon tetra' , glowlight tetras, black neon tetras and long fin neon tetras it really depends on the underbelly. A tetra with a rounded larger belly is female while males have flat under bellies. You can see this when they are side by side. When having young tetras, it is harder to tell, as their characteristics haven't yet developed.