Botia lohachata (Pakistani loach)

I took delivery of six Pakistani loaches last week and
placed them in a snail-infested 15 gallon. They are
delightful, lively creatures. and the snails are now in
scavenger heaven. There is one problem though. Something
has been chewing holes out of new Amazon Sword leaves and
the only other possible candidates are two well-fed black
tetras. This is definitely not a (plant) nutrient deficiency.
Does anyone know if these loaches pose a threat to other
soft-leaved plants? I'd also be interested to know how they
handle salt as they may end up in a slightly brackish tank.