How to tell if my fish are male or female and how old they are?

Males are much smaller than females. Males will reach sexual maturity between 3-4 years of age, females won't be ready until they are 5-6 years of age. You can check the vent of the fish. Males will have an oblong opening while the females will be more circular. In the springtime, mature females will become fat with roe (eggs). During this time of year, you can gentle massage the abdomen of an adult fish, if a milky substance comes out then you have a male. This is its sperm. You can follow this link to find information regarding breeding and the necessary supplies. http://www.aquablueseafoods.com.au/bass-breeding.shtml

There are several species of Tetras and sexing them can be tricky or downright difficult. Neons are the easiest. Look at the neon line along the body. If it is straight, you have a male. If there is a slight curve, you have a female. In other species, it isn't as easy. Females are generally rounded and fatter. Males are longer and slimmer. Male Danios have more vivid and shiny colors than females. Both have yellow between the stripes, but males are more vibrant. Male Danios will also be longer and slimmer while females will be shorter and "thicker". If they spawn, you can leave the eggs and adults in the main tank. The adults will eat the eggs...or fry (baby fish) if they hatch. You can also vacuum the eggs out and discard them.

Dwarf gouramis can be very territorial. If your tank is not big enough, one will chase the other. Removing one fish or transfer to a larger tank may be necessary. You can determine sex by looking at the dorsal fin. The male's dorsal fin is pointed, while the female's is rounded or curved.

The best guess would be an adult. Unless you know the hatch date, it is difficult to be more specific. Adult Bettas are about 3 inches long. They reach this length anywhere between 7 and 12 months of age. His eyes are dark, his color is good and his fins are long. He's at least a year old. That would be my best "educated guess" based on the images provided.

Hello, my name is Dr. Shines and I am happy to help. There's only one photo of the Dalmatian Molly and it looks female but it's blurry. Here's a link with a photo showing a male vs female live bearer (which include mollies, platies and guppies) https://www.fishlore.com/aquariumfishforum/threads/sexing-livebearers-with-pictures.169520/ I hope this helps and please feel free to reach out any time.

If they are at least 12 months of age, you can determine gender by looking at the color of the cere (nose). In males, the cere is a blue color. In females, it is tan/brown. If they are younger, you will need to wait or you can have them sexed by DNA using blood or feather samples.

Male veiled chameleons have a tarsal spur, a heel spur, that is present from hatching. Females do not. Check the back legs for this bump. If it is present, you have a male. There is no definitive method of determining age. Chameleons will grow at different rates. If possible, go back to Petco and ask the associate. There should be records which may contain a breeder/source and a hatch date.