Tetras: tattered dorsal fins

[Momtoast]

I started my tank with four glowlight tetras. Recently I added three more, because I heard they are more comfortable in a larger school.

I noticed recently while watching during a feeding time that some of the little guys look like they've had their dorsal fins nipped or bitten off. This is the only fin on them that looks this way. They are still swimming actively and eating heartily. They don't have any spots or any other sign of illness that I can see.

Do you guys think this is some kind of initiation or badgering by the old four fish I had in the tank because they're the new guys? (Assuming it's the new guys that are harmed, it's a little hard to tell, but they are the smaller ones.) Are the other tetras pecking at them or the Dwarf Gourami I have in there also? I'm not quite sure what to think. Could it be the start of an illness?

:help:

 

[Ripples]

Hey Momtoast

You heard right on tetras. However, there's a few things we need to know before anyone can help you.

First up - what size tank do you have? If you've got these guys in close proximity they may be getting stressed - and the gourami may be taking it out on the tetras.

Secondly - do you know what the ammonia/nitrite/nitrate levels are in the tank? It could be that your water chemistry is out of kilter and this (again!) is causing stress and illness

Thirdly - are you seeing any agression at all? Or are any fish acting weirdly (gasping for breath/not feeding/slothful and not moving as much as normal?

All these will give us some indications on what's happening.

Thanks!
R

 

[Momtoast]

They are all in the 10 gallon tank in my signature. I thought they would have enough room, but I'll admit, that probably is tight for them.

The chemical levels after the last water change (on Monday) were:
Ammonia: 0
Nitrites: 0
I don't know Nitrates. For some dumb reason, my test kit didn't come with it. Also, I think my pH might be a bit high, around 7.4.

All the fish are still very active. None are slothful or gasping for breath. The tetras stay away from the Gourami for the most part, unless they're all eating. They play with each other a lot.