ZebraPleco.com • The complete Hypancistrus zebra resource

As soon as I did water change, one zebra went into the cave in which another male zebra was guarding. usually the male guards his cave and not allow anyone get in, and this time is different. it's been hours that they still stay together. I think there might be an sign of spawing. but when i paid more attention, the zebra who went into the cave was a male. Though I'm not sure about the sex. I posted a pic here and people told me that it's a boy. then I got further confused.
Can someone tell me what positions the male and femlae should be. male inside or female inside? if there is a spawn, how long should they spend together? Thanks for you all!

That's a good sign. If it was a male then other male who 'owns' the cave would not have let it in...so it's more than likely a female. Sexing zebra's is not easy and just because the general concensus says male doesn't mean it definitly is. Actions speak for louder than words in this instance...so if it's acting like a female then it probably is.

In answer to your ' which order in the cave' question, the male should have the female trapped in the cave until she gives up her eggs. So the female should be furthest into the cave with the male nearest the exit so he can block her in. Spawning can take several days... for a more specific answer have a look for other topics in this forum explaining the same thing, there are several. Or even click on the breeding link under the home link at the top of the page. It's all there!