blenny gender/maturity questions

[DanSavesTheDay]

I purchased my two Molly Miller Blennies a few days ago and noticed by the next day how different the two had appeared. The larger and darker one seems to be more aggressive and has a much more vibrant color to it. The other seems somewhat light colored and pants open mouthed.

From these pictures can anyone tell me if this is a maturity difference or a gender difference? Or could they not be the same type of blenny?

Thank you in advanced for your responses

 

[JasonK84]

The greenish yellow one is georgeous!! I'm thinking male? The other in the picture on the powerhead mount appears to have ich!! Not sure of male or female though.
Here is my molly miller (I actually have three)

 

[DanSavesTheDay]

The greenish yellow one is georgeous!! I'm thinking male? The other in the picture on the powerhead mount appears to have ich!! Not sure of male or female though.
Here is my molly miller (I actually have three)

I will keep an eye out for it and double check. It usually kicks up tons of sand and swims up onto the power head from the side. It seems to be eating normal grazing like a cow the greenish yellow one just sits inside it's shell most the time guarding its territory.

I will check in the morning when he's out and about to see if those spots are on his fins for sure and looks into an ich treatment or setting up a QT tank for him.

Also here is a picture of the Blenny in it's shell. It's even happier now that I've turned it upright today, so that it can shoot directly up or at an angle.

 

[JasonK84]

I will keep an eye out for it and double check. It usually kicks up tons of sand and swims up onto the power head from the side. It seems to be eating normal grazing like a cow the greenish yellow one just sits inside it's shell most the time guarding its territory.

I will check in the morning when he's out and about to see if those spots are on his fins for sure and looks into an ich treatment or setting up a QT tank for him.

Also here is a picture of the Blenny in it's shell. It's even happier now that I've turned it upright today, so that it can shoot directly up or at an angle.

Very nice coloring on that one!

 

[eatbreakfast]

The nice colored one is dominant and likely male. However, molly millers are fairly intolerant of conspecifics, so being poorly colored and stressed will make determining gender difficult.

 

[Jposch]

The nice colored one is dominant and likely male. However, molly millers are fairly intolerant of conspecifics, so being poorly colored and stressed will make determining gender difficult.

I'd have to disagree. I have 28 of them, spread across 3 tanks, and aggressive was mild for maybe a week before it subsided almost completely. Any unwed fiah will turn into a terror. Highest density is 6 in a 90 gallon. Mixed sees. Id liken any interspecies fighting to household cats. Mostly harmless dominance displays. A much lower risk than many other atockjng ideas.