What kind of fish should I get?

[LBDave]

So my 20+ year old silver dollar just passed. I'm thinking of getting a fish for this tank to cheer us up.
There are 3 silver dollars in the tank. One male and 2 females. One is a spotted. She is ok with the other 2 but a little smaller. She doesn't spawn with the male. The other does.
The SD's are about 2 years old.
I have 6 congo tetras. One male and 5 females. They are about 2 years old.
The tank is 4'X 18" X 30"high. My water is HARD and Ph 8.1+
ALL THESE FISH ARE VORACIOUS EATERS. Tetras at top mostly. SD's eat everything everywhere.

So any new fish would have to compete with that. Not sure a catfish would get enough food. Or an earth eater. SD's are just so voracious.
I am looking to get ONE fish. Don't need pecking order issues.

(If I got more smaller fish this isn't my first choice.)

I'm really looking to get a little personality in the tank if possible.

 

[Fish seeker]

depends on what tank you have

 

[LBDave]

depends on what tank you have

duh read my post

 

[Fish seeker]

red tailed black shark

 

[LBDave]

red tailed black shark

I'll give you some slack. You're probably new. Red tail black sharks can be aggressive. I'm leaning towards at geo.

 

[Deadeye]

Maybe a firemouth? Does the same job as the eartheater but would be more suited to the hard alkaline water.