I had a skunk loach in my tank with a few other community fish, incl corys and snails - but as soon as I added my 4 bristlenose he chased these until he killed one and seriously harmed the other, which died after a day - I have removed the skunk loach to give my other two bristenoses a break, Is this common? I did have 6 of my borneos die unexpectanly when I introduced him - he is about 10cm