Hi--as an update, this loach immediately calmed down after that first day of nipping at any fish that went close to him. He is mostly a ground-feeder but occasionally goes up to the surface to feed with the rest. He hasn't bothered anyone since. So he seems to be a good addition to the tank.
The algae eater I have is a smaller kind--not sure of the exact type...and the catfish stays tiny as well.
The one fish in my tank that is a complete mystery to me is my puffer. I have never seen him eat ANYTHING in the past 6 months he's been in the tank...but there are tons of dead snail shells all over the tank...and one time I saw him peck at a snail but never eat it. I keep buying 10-20 snails every couple of weeks putting them in the tank assuming he is eating them....but WHEN??? All he does is float around in that weird hovering puffer way. A very fascinating fish to watch. DO you think he is eating the snails