Skirt tetras hiding from serpae

[Alliestars]

Hello, I have a 30 gallon tank with 5 High-fin skirt tetras, one phantom tetra, and 2 of what I think are called Chinese algea eaters. Recently I purchased 2 serpae tetras not actually knowing what they were (there was no tag and they gave me a random price. I probably should not have purchased them from this location, but I knew they were tetras). I was hoping they would get along with my phantom as I can not find more of him at any local place. Unfortunately I did my research when I got home and found out serpae aren't the friendliest but I assumed my big skirts would put them in their place. However, I noticed that all of my skirt tetras are hiding in the back of the tank and usually they are quite friendly. The only active swimmers are the serpae and it used to be my skirts. The little phantom is not bothered at all. Now my question is, should I try to buy more serpae tetras to ease the possible aggression going on or should I take them back completely and find more passive fish/ stick with what I have. I like the serpae a lot, but not if they will forever harass my current fish. Thanks!