Rosy barbs skinny and pale

[W.J.]

Hi,

I have a 57l tank (fluval flex) with two neon tetras, five (now four) Rosie barbs (3 male, 2 female) and two Mystery Snails. I suspect the neons think they are rosy barbs. We got the Rosies about five or six weeks ago. They are our newest addition. Before they arrived, we lost a few neons to "loopiness" (erratic swimming and the inability to stay upright, then they die). But the remaining few cheered up considerably when the Rosy Barbs arrived and seem healthier than ever.

One of the male Rosies started looking very skinny and his eyes were bulging. He has since died. Another male rosy is also looking quite pale and thin, but not as bad as the first (yet). The third male rosy looks spectacular. Very rosy. Not skinny at all. The females are suspicious round and I wonder if they are carrying eggs. 

Is this normal for spawning time or is it stress or a disease of some kind?

How can I tell?

We don't have a quarantine tank, unfortunately.

[Caryl]

All tetras are schooling fish so are happiest in large numbers. They are happy to join other schools of fish - safety in numbers.

When narrow fish get skinny if oten makes their eyes look bulgy. The females will carry eggs in varying numbers most of the time so if you have one spectacular looking male (who may have harassed the other males, you don't say what sex ratio you have) they will be getting their eggs ready in anticipation.