Yoyo Loach Known To Kill Other Fish?

[roku.g9]

i recently bought a yoyo fish.
i then properly put it into my 10 gllon tank with my glass catfish three platies and two goupies. After leving the tank for several hours i come home to find a dead goupy.
i inspected the body and found a redish pink spot on it. I also noticed a mickey mouse platy had a pinkish red spot too and sort of a green spot. The tip of the yoyo fish has red spikelike things. Its not known to be a harmful fish and i need to know if it is because if it is i need to take it out of my tank immediatley. thanks

 

[bitteraspects]

i have never known of one to be aggressive and attack other fish

 

[MBOU]

If you had said the tails, id have said yes or maybe, i've seen them be really nippy with long finned fish...

 

[Curiosity101]

I wouldn't expect the problem to have come from the loach to be honest.
I'd have thought this has more to do with the tanks set-up.

For example a glass cat is too big for 10gal
As is a YoYo Loach, also they should be kept in groups.

How long has the tank been set up?

How did you cycle?

What are the tank stats?