Black outline on fins? w/ pic

[Ficious]

whats the general cause of this? my 55 gallon tank has two penguin 400's and theyve been established for months. theres never any ammonia in the tank and nitrates are between 20 and 40 sry not sure about nitrite(out of that one). temp is 78 degrees and the stocking is 2 juvi oscars, 3 inland rainbows, L201, whiptail plec, and raphael cat.


i do keep up on water changes...about 25% per week.


the black shows up on some fish put in there and some fish it doesnt show. one of my O's fins grew back as black and its an albino tiger.

 

[Citrinellus]

Its common for "albino" oscars to have black on their fins. The black on my oscar's fins is starting to fade away. Also, they're not albino their leucistic.

 

[peewee]

my silver dollars does have that every night, i wonder what that means.

 

[Lupin]

my silver dollars does have that every night, i wonder what that means.

In your case, fish can shift colors around depending on their mood and environmental conditions. A lot of fish show faded colors when they become inactive at night.