I have a 24 gallon and usually have six small fish. A year ago I had a Pajama Cardinal about 4 years old, a Clown Goby about 5 years old, a Firefish about 3 years old and a Bicolor Blenny about a year old.
So I decided to get a pair of Hi Fin Cardinals and one really dominated the other. So I sold the dominant one. Then the remaining Hi Fin became bossy and My Pajama Cardinal would not come out and the Firefish rarely came out so I sold that Hi Fin.
The Firefish came out and stayed in the middle most of the day. It took The Pajama Cardinal about 4 weeks to come out and even then it was very skittish.
I decided to add an Orange Striped cardinal so rather than 2 I decided on 3 and I also went for a Black Axil Chromis. The Chromis is around the size of the Pajama and is active. The Pajama Cardinal now is out all day protecting his little corner
from the Chromis. Didn't expect that. The firefish is hiding. I think the Blenny unnerves him. The Blenny is moving around much more and doesn't seem to like the fact that there
is more competition for him. The Orange Stripes are very small, maybe 3/4 of an inch. But their mouths are very big. They compete for the food
and can really eat some big pieces. As of now they look yellow rather than orange. Probably will not be able to keep all three when they are full grown.
They stay together near the bottom and don't seem to mind that they are smallest in the tank. When food is there they go to the top besides getting it from the water column.
