Whats Wrong Here? New Fish Die

[Ricky Savage]

I have a 10g tank, orginally it had a small school of white skirt tetras and neon tetras in it, this set up last about 6 months with no problems, but one by one the fish would die, eventually leaving a healthy single white skirt tetra left. He stayed by himself for a few months, seemed very strong, eventually i added a small school of serpae tetra(5), and a group of Autralian Rainbows(4) in with him. At first everything is ok but after a little bit i realized that the lone white skirt chased and harrased the serpae's and occasionally attacked the Rainbows. Eventually the school of serpaes died and 3 of the rainbows would show up dead as well....the lone rainbow and tetra attack eachother ocassionaly but usually keep out of eachothers way. but as of recently the rainbow fish looks somewhat sickly and has some sort of spasms every now and then.

My question is what is wrong here?....is the white skirt too agressive towards the other fish, causing them to stress out and die?...or because of the weird spasm's does the water have parasites?

 

[DiscusKeeper403]

ok well your tank is overstocked. i mean rainbows can get pretty big. the aggresion is probly caused by the lack of space and teritory.