Why is my guppy doing this?

I have a four male guppy’s in a ten gallon tank, I noticed after adding the other two guppy, that my black male guppy is backing up and shaking his tail at the other guppies. Especially the red one. Is this dominance? I’ve also noticed that the “red” guppy has a split tail as long as a ragged is bit. Should I be concerned is it just dominance.

 

It's a sort I'd showing off move primarily for the ladies, but they'll for each other if there's no females around.

 

Lol okie, what should I do for the shredded tail?

 

Just keep your water nice and clean and let it heal. Tears just happen sometimes and often heal fairly quickly so there isn't some aggravating factor.

 

Well, ok. It keeps getting worse, but it’s not finrot.

 

Best thing to do is fill out the template to give people the full picture. Aquatic Emergency Template | Freshwater Fish Disease and Fish Health Forum | 376562

 

Best thing to do is fill out the template to give people the full picture. Aquatic Emergency Template | Freshwater Fish Disease and Fish Health Forum | 376562

I already did

 

I already did

In which thread?
Lets merged them so the info is all in one place.

 

In which thread?
Lets merged them so the info is all in one place.

Oops lol, got mixed up with one of my threads:
What is the water volume of the tank? 10 g
How long has the tank been running? 1 and half years
Does it have a filter? Ye
Does it have a heater? Ye
What is the water temperature? 75
What is the entire stocking of this tank? (Please list all fish and inverts.) serpae tetra, 4 guppies and a golden snail

Maintenance
How often do you change the water? 1 every week.
How much of the water do you change?25 percent
What do you use to treat your water?
Do you vacuum the substrate or just the water? Both

*Parameters - Very Important
Did you cycle your tank before adding fish? Ye
What do you use to test the water? API test kit and test strip
What are your parameters? We need to know the exact numbers, not just “fine” or “safe”.
Ammonia:0
Nitrite:0
Nitrate:2 ppm
pH:6.5

Feeding
How often do you feed your fish? 1 day beside one skip through week
How much do you feed your fish? As much as they eat in two mins
What brand of food do you feed your fish? Topfin
Do you feed frozen?no
Do you feed freeze-dried foods?ye

Illness & Symptoms
How long have you had this fish? 4 months
How long ago did you first notice these 5 days symptoms?
In a few words, can you explain the symptoms?
Have you started any treatment for the illness?
Was your fish physically ill or injured upon purchase?
How has its behavior and appearance changed, if at all?

Explain your emergency situation in detail.
(Please give a clear explanation of what is going on, include details from the beginning of the illness leading up to now) twitching tail , and backing up, pecking at other guppies.