Aggressive female mandarin

[steallife904]

I have had a male and female mandarin dragonet for about a year. They where together in the same tank when I bought them but where not bought as a mated pair. They never had any issues with each other until recently. on sunday I walked up to the tank during the day to look and saw that the female and the male locked in her mount (male was upside down). I reached in and separated them, the male took off but she chased after him, I decided to put some Mysis in the tank and she went for the food and he swam away and hid. Well I haven't seen him since.... I have seen her. Now the tank is big so sometimes it can be a few days before I do find them swimming around the rock but I fear she killed him

What would cause her to turn on him all of a sudden??? I did notice she caught up in size to him, maybe even a hair bigger. Would this cause her to flip a switch?

 

[ThRoewer]

What size are they?
Are they both of equal size?

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[steallife904]

yes both about equal. if I had to guess I would say the female got bigger by a bit than the male.

 

[ThRoewer]

That's the reason!

Mandarin males need to be significantly bigger than the females or the females won't accept them as mates. They usually just ignore them.
But if a smaller male tries to mate with an equal sized or even larger female and doesn't get the message or even gets pushy the female will get aggressive.
I had the same with my pair at the beginning. By now the male is at least a third longer (= twice as large) than the female and everything is fine.