All guppies chasing one guppy!

I've noticed this morning all my guppies and endlers are constantly chasing 1 guppy, non stop!
Why could this be? I have made sure all guppies I get are male but I'm wondering if I could have be sold a female? This guppy is very colourful and no different in size to the rest so doesn't look female! What other reason could there be for this behaviour and should I intervene?

 

Is it sick and injured, a picture would help.

Is there a gonopodium on the guppy being chased?

 

I have now removed the fish as they seem exhausted and its not stopping.

 

it is a male

His tail his broken due to nipping?

 

I don't think so.

He doesn't seem sick!
Swimming fine, ate this morning and no physical signs.

 

Tanksize? Water parameters? Full stocking?

 

You could just have some aggressive fish, my males are quite aggressive and they fight one another quite often. They could be fighting for dominance.

 

Do you think my guppies have black spot disease?

 

Do you think my guppies have black spot disease?

Could you answer jkkgron2's questions?

 

Tanksize? Water parameters? Full stocking?

100 litres
Nitrates 10
Nitrites 0.2
Ph 7.6
Temp 25.4

Stocking
4 guppies
4 endlers
6 corys
5 neon tetras
5 harlequin rasboras

Sorry the replies didn't show up before!

 

100 litres
Nitrates 10
Nitrites 0.2
Ph 7.6
Temp 25.4

Stocking
4 guppies
4 endlers
6 corys
5 neon tetras
5 harlequin rasboras

Amonia?

 

100 litres
Nitrates 10
Nitrites 0.2
Ph 7.6
Temp 25.4

Stocking
4 guppies
4 endlers
6 corys
5 neon tetras
5 harlequin rasboras

What’s the ammonia?
Edit: The endlers may be the culprits: they’ve been known to nip guppies.

 

Sorry ammonia is 0
Does it look like they have black spot?

 

Sorry ammonia is 0
Does it look like they have black spot?

It looks like he’s being bullied. You could try adding in more decor to break up the Territorys/space so that he has more places to hide.

 

If he is the largest male in the tank the others will try to breed with him because bigger means more babies (except no babies occur because it's a male).

 

If he is the largest male in the tank the others will try to breed with him because bigger means more babies (except no babies occur because it's a male).

He is the largest! That makes a lot of sense. I just feel so sorry for him, he's not getting a break!