It is very easy to distinguish between male and female mollies. Female's body are more round while the male's are slender in shape. Also females have fan shape anal fin while the males have more developed fin known as gonapodium.This is key feature to distinguish between them. The above image is of male while female molly have fan like fin which you can look in lower image. Molly' fishes are available in wide varieties and every species shares same body characteristics.
Tip of the day
Tips for purchasing fish tank air pumps
Larger fish tank air pump will generate more heat, it's not always that the larger is better. Go according to need. Also fish tank pumps produces lot of sound so test them before hand. The heat production by larger air pump will be more.
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