Glowlight Tetra Inflicting Damage Upon One Another, Why?

So when I first bought these guys I only bought 5 and worse only placed them in a 10 gallon but through months of saving up money I was able to move them to a 20 gallon and add another one. But I still see them fight another every once in a while. Two individuals seem to encircle each other in an intimidating way before pecking each other in a quick manner. Other times they nip each others fins and you can see a chunk of the fin missing where the bite mark was. Is it normal for this to be happening or do I just have "rogue" tetras? I have asked this a couple months back when I first got them but was told that this is their hierarchy. I currently cannot take pictures as my camera isn't working.
ps: the fighting are sometimes in a similar fashion to these neons here

 

It might be that you have the wrong ratio of males to females or simply that the females are in breeding condition and the males are fighting over them.

 

Ive seen injuries on both males and females so I don't know why that is happening.

 

Are they all the same kind?

 

yes, for sure they are all glowlight tetras.

 

Sorry, don't know where my head was! I have glowlights but I was thinking of Glofish!

 

Do you know why this is happening or have any solution to it, I mean I feel it is weird for them to be ripping each others fins off. Sometimes when I drop food, one fish kinda darts up and down but doesn't get it in fear of the the other indivduals because sometimes when it does get the food it ends up getting nipped the the other fishes.

 

Well let's try checking things off one by one.

What is the tank setup like?

What are your parameters?

Any other tankmates?

Any changes recently?

 

its a planted tank that's been established for maybe 6 months. Currently the only other tank mates are cherry shrimp. There have not been any new changes, the fighting has happened since the week I got them which was close to about 9 months ago

 

Do you have a test kit? A thermometer at least?

 

yes I have the ApI master test kit and I test weekly, every time I do my 25% water change. I have a thermometer and the tank is set at 77 degrees.

 

Great! So what are your current parameters?

 

Ammonia:0 Nitrite:0 Nitrate:20 ph:7.8 .

 

Here is an old trick for handling the normal hierarchy fights fish have - if you can, increase the water flow. Sometimes, it is almost as if excess energy is behind actual biting. If there is a flow area in the tank, like a stronger filter outflow, they often burn off energy there. It isn't a fast water species, but most tanks are close to stagnant.
I had glowlights do the sparring dances, but I have never seen damage. it's a species I really like, so I have had them quite a few times.