What do you think?
So i have a 20gal long with male guppies which have been together for quite some time now, they chase eachother but have never nipped or been aggressive, and about 4 months ago i got a couple bumblebee gobies ( they were house in with the guppies at the pet store so assumed they were ok with them) and they stayed on bottom mainly and never bothered or chased the guppies, well I have noticed recently that one of the gobies now swims up by the guppies during feeding and chases them which I do feed them on different sides of the tank, have plants and bottom is also grass type plants and driftwood, but i have recently just noticed one of my guppies has half its back tail missing, well I thought it was from the incident of my light falling into the water while it was turned off when I was gone for weekend camping, (lost couple guppies due to it) but now i just noticed this guy in the video that has the whole top dorsal fin completely ripped off and he wasnt like that yesterday....is it more than likely the gobie?? And I do have a glo light tetra seen in the video, ember tetra and a neon that have never paid no mind to the guppies and they have been in there for over a year now, (their buddies died a while back and I decided I was just going to have guppies once the last few tetras end up dying) just looking for some advice, I will remove the gobies if its believed they could be the culprits!