After posting and then re-reading:
Sounds pretty normal, s/he's made that spot their territory, and only chases off others when they invade it. Just an adult doing it's thing and protecting their spot in the tank!
If you can't manage a bigger tank, a 30g would be perfectly fine for a group of dwarf chains. But I would, sadly, suggest returning the two yoyos, and searching for more dwarf chains so the single dwarf chain has conspecifics, and will suit your tank size. I truly think two yoyos is a bad idea long term, for them and others in the tank, since without a large enough group, they'll dominate each other, and take it out on other tank mates too, especially a smaller dwarf chain. They'll annoy the hillstream too, and likely any upper level fish you have.
But a 30g is too small for even two yoyos, and they need a group too, which means a bigger tank.
I'm genuinely sorry if it's not what you want to hear, and of course, it's your tank, and your decision. That's just my two cents.
I think honestly the greatest aggressor at the moment is my hillstream loach who often attacks the yoyos. I have no idea why she has become so aggressive, she used to just hide under her slate, but its not a active aggression she only does it when they get close to her.
Sounds pretty normal, s/he's made that spot their territory, and only chases off others when they invade it. Just an adult doing it's thing and protecting their spot in the tank!
If you can't manage a bigger tank, a 30g would be perfectly fine for a group of dwarf chains. But I would, sadly, suggest returning the two yoyos, and searching for more dwarf chains so the single dwarf chain has conspecifics, and will suit your tank size. I truly think two yoyos is a bad idea long term, for them and others in the tank, since without a large enough group, they'll dominate each other, and take it out on other tank mates too, especially a smaller dwarf chain. They'll annoy the hillstream too, and likely any upper level fish you have.
But a 30g is too small for even two yoyos, and they need a group too, which means a bigger tank.
I'm genuinely sorry if it's not what you want to hear, and of course, it's your tank, and your decision. That's just my two cents.