The diagnosis is not confirmed yet, but the probability of it being whitespot is quite low, given the salinity of the water (it's now finally SG 1.002 @ 25 C). I have just discovered it, and tomorrow morning I'll look at it again, hopefully being able to exclude the whitespot scenario. Apparently, not much can be done against lymphocystis, apart from letting it develop, and hopefully die out, but it is a virus, and in the small confined environment of the nursery where the glassfishes are kept, it may spread... :-(
Meanwhile, I got probably the best picture of these little guys:
Meanwhile, I got probably the best picture of these little guys: