Male or female?

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Satanoperca are not sexually dimorphic, venting or observing the breeding tubes are the only way to tell.
 
This is a late response, but I have found my S. leucosticta to be subtly but reliably sexually dimorphic. All my females all have more red in them and are rather more colourful than the males overall. The males have slightly longer trails in the dorsal and anal fin (but remember sometimes those get bitten off during squabbles).
 
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