Oscar fish behaviour and sex type

Question
My two oscar fish approx 11 and 13 mths old are now cleaning rocks with their mouths and trying to lift one of the rocks.  Do both male and female oscar fish display this behaviour? Shall I remove the rock one of the oscar fish is trying to lift with its' mouth? If this is part of the breeding behaviour, how soon after do they lay eggs?  How often do Oscar fish lay eggs?  One of my fish has an obvious tube pointing down from its groin about a mm or so long and I have noticed this over the last few weeks, this is the older oscar.  The younger oscar does have a tube also I think but it is much smaller and doesn't show obviously like the other oscar.  Do you think I have two opposite sexed oscar fish? I am hoping that you can give me some answers from a very excited oscar owner!

Answer
Hi Lee,
 It sounds like you have a pair of oscars that are just about to lay eggs. Definitely do NOT remove the rock!  Let them do their thing.  

-- Ron
  rcoleman@cichlidresearch.com
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