Aggressive silver dollar

[beatle]

I have 2 silver dollars in my tank, a male and a female. They're both full grown @ 4" (female is 9 years old, male is unknown). They're just getting to know each other now, and the male is being very aggressive towards the female. Last night I found bits of her tail fin missing, and this afternoon I found that it is gone entirely.

She's active in the tank now, but she hid behind driftwood when I first introduced her. Aside from the harassment from the other silver dollar, she seems better. She eats the veggie flakes and doesn't hide from the male.

The other tankmates are a 4" angelfish (he harasses the male silver dollar from time to time, but doesn't bother the female much) a 2" cory, and a 6" pleco. They're in a 29g with driftwood and plastic plants.

How long will this behavior continue? Should I separate the female? :huh:

 

[Roan Art]

What kind of dollars are they?

4" is not a full grown silver dollar. If they are full grown and only 4" then they are stunted. Silver dollars, the smaller spotted ones, grow to 6-8". The unspotted ones 8-10". Have they always been in this 29g tank?

They are schooling fish, you know, they really need to be in schools of six or more. It's not unusual for one to take a dislike to another, but if they are in a proper school there are more of them for him to pick on.

Are you sure the angelfish isn't picking on her?

Roan

 

[beatle]

They're not spotted or red hooks. They appear to be plain jane silver dollars. The angelfish rarely picks on her. The male silver dollar does it like there's no tomorrow.

I received both of these fish with used fish tank purchases. The male was by himself (as far as I can tell) in a 20g tall for a few years with the angelfish, the cory and the pleco. The female was in a 55g with another dollar of the same age and a convict - both of which died shortly after the move.

As far as adding other dollars to the tank to provide a proper school, a school of 6 isn't possible in a tank this size, and I'm not going to be moving them to my 55g when they grow up. Also of note is a darker spot behind the male's gills. I've read that this comes and goes and sometimes indicates breeding behavior.

 

[Roan Art]

The "plain jane" ones are the ones that grow 8-10". I've one we got in August that was about the size of a silver dollar. He's 4" now. The new ones we got a month ago have doubled their size.

They're way bigger than the three spotted ones we have that are the same ages.

I'm not pointing fingers at you -- you bought yours "used". Mine were in a 20 gallon until Jan 4th and I bet if they had stayed there they wouldn't have gotten much bigger at all. They were our first fish and, of course, the LFS didn't tell us that a 20g was too small.

Now theyre in a 65g and they'd better grow, pronto!

To the problem at hand -- it's possible he might be picking on her because he's being randy, but knowing that doesn't solve the problem. Perhaps he's being territorial?

What might help is if you remove them both for a bit, change the tank decor around -- making sure they both have hiding places, then put them both back in at the same time. If he's being territorial, it'll be like he's in a whole new tank and perhaps he and her can work out their differences.

Might be worth a shot.

Roan