My mollies are turning black

[fishtankfish]

I have two balloon bellied mollies which i love very much in my ten gallon tank. I had the male first and after about 2 months he started to get black markings the end of his fins. He got about 4 distinct black marks and no more. Now, my female which is a more recent addition is starting to get the same black markings. The spots dont seem to be harmful or affecting the fish in anyway. I just am curious what causes them and perhaps if they could be bad for my mollies. Thanks.

 

[Keeper]

It's probably just them "growing" up. As most fish grow, they will start to display different colorings and new markings.

 

[RandomGuy]

It may be a case of color pigmentation.. lol hope that helped..

 

[Menagerie]

fishtankfish, please provide the water parameters.

 

[fishtankfish]

I dont have them exactly (what do you guys use to get them) but i tested the water and all parameters are in the healthy range, with the water being slightly hard.

 

[Menagerie]

Liquid test kits are best. Ammonia and nitrite should be 0 and nitrates below 40 ppm.
If the fish are doing fine and it is just a case of maturation, things are fine.