Rainbowfish sexing
- Thread starter Unladylike
- Start date
Both males.
Melanotaenia praecox (neon rainbow), males have red fins and red tail, females have yellow or orange fins and tail.
Melanotaenia lacustris males get deeper (higher) in the body and have longer more pointed fins.
First dorsal fin
You can sex most species of rainbowfish by looking at the fins. The first dorsal fin on males should overlap the start of the second dorsal fin. This is always the case with good quality fish and wild caught fish. If the fish are inbred and have poor finnage, the males first dorsal fin won't always overlap the second dorsal fin but it should touch it.
The first dorsal fin on female rainbowfish does not touch or overlap the second dorsal fin.
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Second dorsal fin and anal fin
The second dorsal fin and anal fin on males will be longer and more pointed than the female's fins, which are shorter and more rounded. The male's second dorsal and anal fin usually touch the tail, whereas the female's fins don't. Again though, this can vary depending on the quality of the fish and some poor quality males have short dorsal and anal fins that don't touch the tail.
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Dorsal blaze
If the fish are displaying to each other, you can look for a dorsal blaze on the males. This is a coloured stripe that runs from the start of the first dorsal fin down to the nose. Male rainbowfish produce a dorsal blaze when displaying or breeding. The females never produce the coloured stripe.
The dorsal blaze will vary between the different species of rainbowfish. Melanotaenia lacustris usually has a yellow dorsal blaze. I think M. praecox does too but not 100% on that. Other species have a white or pink dorsal blaze.
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Body height
The males of most rainbowfish get deeper (higher) in the body than the females. With young fish this is not easy to see but when the fish are more than 1 year old, it can be easy to see.
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The M. praecox in the picture has a few scales missing on the side of the body. This might have happened if the fish swam into something or got stuck and ripped a couple out. However, it can also be the start of rainbowfish ulcer disease, which are ulcers normally caused by Fish Tuberculosis (TB). There is no cure for Fish TB and once it's in a tank, it is there until you scrap the tank and start again. It also infects all the fish in the tank and rainbowfish are regularly infected with it.
Unless the shop can guarantee the fish doesn't have TB, I would probably avoid both fish.
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Feeding
Rainbowfish need lots of plant matter in their diet and at least half of their diet should consist of plant/ algae. You can offer them marine algae from Asian supermarkets, aquarium plants (Duckweed is taken by most rainbowfish), algae/ vege flakes, wafers and pellets. You can also offer them bits of cucumber, zucchini, pumpkin and other fruits/ veges you offer suckermouth catfish.
Avoid frozen bloodworms because some brands can cause problems to rainbowfish. Freeze dried bloodworms are fine but avoid the frozen ones. You can feed rainbowfish on other types of frozen (but defrosted) foods including brineshrimp, daphnia, mysis shrimp, prawn, fish, squid. They will eat most insects too and as long as the insects are free of chemicals, they are fine to use.
The following link has all the known species of Australian & New Guinea rainbowfish and tells you where they come from and how to sex them.
rainbowfish.angfaqld.org.au
Melanotaenia praecox (neon rainbow), males have red fins and red tail, females have yellow or orange fins and tail.
Melanotaenia lacustris males get deeper (higher) in the body and have longer more pointed fins.
First dorsal fin
You can sex most species of rainbowfish by looking at the fins. The first dorsal fin on males should overlap the start of the second dorsal fin. This is always the case with good quality fish and wild caught fish. If the fish are inbred and have poor finnage, the males first dorsal fin won't always overlap the second dorsal fin but it should touch it.
The first dorsal fin on female rainbowfish does not touch or overlap the second dorsal fin.
-----------------
Second dorsal fin and anal fin
The second dorsal fin and anal fin on males will be longer and more pointed than the female's fins, which are shorter and more rounded. The male's second dorsal and anal fin usually touch the tail, whereas the female's fins don't. Again though, this can vary depending on the quality of the fish and some poor quality males have short dorsal and anal fins that don't touch the tail.
-----------------
Dorsal blaze
If the fish are displaying to each other, you can look for a dorsal blaze on the males. This is a coloured stripe that runs from the start of the first dorsal fin down to the nose. Male rainbowfish produce a dorsal blaze when displaying or breeding. The females never produce the coloured stripe.
The dorsal blaze will vary between the different species of rainbowfish. Melanotaenia lacustris usually has a yellow dorsal blaze. I think M. praecox does too but not 100% on that. Other species have a white or pink dorsal blaze.
-----------------
Body height
The males of most rainbowfish get deeper (higher) in the body than the females. With young fish this is not easy to see but when the fish are more than 1 year old, it can be easy to see.
-----------------
The M. praecox in the picture has a few scales missing on the side of the body. This might have happened if the fish swam into something or got stuck and ripped a couple out. However, it can also be the start of rainbowfish ulcer disease, which are ulcers normally caused by Fish Tuberculosis (TB). There is no cure for Fish TB and once it's in a tank, it is there until you scrap the tank and start again. It also infects all the fish in the tank and rainbowfish are regularly infected with it.
Unless the shop can guarantee the fish doesn't have TB, I would probably avoid both fish.
-----------------
Feeding
Rainbowfish need lots of plant matter in their diet and at least half of their diet should consist of plant/ algae. You can offer them marine algae from Asian supermarkets, aquarium plants (Duckweed is taken by most rainbowfish), algae/ vege flakes, wafers and pellets. You can also offer them bits of cucumber, zucchini, pumpkin and other fruits/ veges you offer suckermouth catfish.
Avoid frozen bloodworms because some brands can cause problems to rainbowfish. Freeze dried bloodworms are fine but avoid the frozen ones. You can feed rainbowfish on other types of frozen (but defrosted) foods including brineshrimp, daphnia, mysis shrimp, prawn, fish, squid. They will eat most insects too and as long as the insects are free of chemicals, they are fine to use.
The following link has all the known species of Australian & New Guinea rainbowfish and tells you where they come from and how to sex them.
Melanotaeniidae and Pseudomugilidae
A website dedicated to Rainbowfishes of Australia and New Guinea
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