Mylosoma Aggression?

[Scatocephalus]

About 4 years ago I bought 4 Myleus rubripinnis and placed them in a 60 gallon tank. I figured they'd be fine as they were only 2"-3" ea. Fat chance. The two largest fish hounded the two smaller fish until they just hid in the corner. They wouldn't even come out to eat. I had to seperate them. Then the largest fish started in on the the next largest. I eventually transferred the two biggest fish to the 125 where they got along as the smaller fish could get away.

Silver dollars are nastier with each other than I would have ever thought.

 

[Scatocephalus]

hey, i recently just got 5 and they are in a 15 tall and no problems at all.
do they look like this:

This looks like a very small Mylossoma duriventre. They've been popping up in the hobby in recent weeks. It's a pretty cool fish but a little more aggressive even than the Myleus species. It is commonly called a Hard-Bellied Pacu.

Jer, just a hunch but the fish with the body spot are the four smallest fish?
Your smaller fish with the spot is the same specie. They start off with the spot, then transition into stripes eventually losing all body markings and turning silver.

Here's the best pic I can find of a small specimen

Here's a few in between stages. You can see the stripes.

It's a nice fish regardless.

 

[Scatocephalus]

Actually, after a bit of research I don't think guanl23's fish is M. duriventre. It is definitely a Mylossoma species but not M. duriventre.

Now, with that said, I think Jer's fish is M. duriventre.

Also, I lied. The adult fish I posted is not M. duriventre but rather M. aureum. M. duriventre is not so golden.

 

[Peanut_Power]

Thanks Mark!

Actually, there are a few with the spots that are larger than the other ones without the spots. So I'm still thinking there are two different species. The bodies shapes are totally different.

The largest one with the spot is indeed starting to get the red on the gill plate, anal, and caudal fin.

I'll just have to snap a few pictures of each of the larger ones and post it up. I'll try to take some tomorrow and upload them for better ID. They are larger and less timid now, so pictures should be easier.

 

[fishmamma]

The one's I told you about, look just like this one... peace!!