My linkei, quindecim and tweediei eat frozen food from the block when I hold it in their tanks, which you could consider trusting the hand feeding them.
To my experience, shyness strongly depends on species, tankmates, but even more on the tank setup and the feeding hand’s owner. I kept my first paro’s (some bintan-like type) in a 25L tank full of oak leaves. There was more place to hide than to swim and I never saw my fish. After a while I considered them dead, so I moved the tank’s contents to my 100cm tank. When moving, I discovered the pair still existed, but moved them anyway. It was not very long later they started swimming around in the meter tank, not worried at all about my presence… They started breeding soon hereafter.
P. linkei never seems shy, not even in shops. P. quindecim idem. I have two pairs of tweediei, in two different tanks. One tank consists of some stones, moss, and a few leaves. The other tank is full of stones(forming caves), Sagittaria subulata(a grassy plant) and Lilaeopsis. Too much hiding space, apparently, for I seldom see them, and when they see me they disappear.
It is also very important how you behave in front of your paro’s. If you press your nose against the glass they’ll feel observed and dart away, but if you sit down in front of the tank and watch for around ten minutes, they will come out of hiding and start doing the things paros use to do.
Combine these factors, and you either never or always see your fish.
@Peter
Most crypto species I try do actually survive and grow, even in my most acidic and dark tanks. I always lose their names, but some green species grows in a tank I can only see my Betta hendra(a super-shiny species) when they’re at the front glass watching me (which seems to be their hobby… It’s a strange feeling, being observed by the creature you’re observing…), and still I only see their colour with a flashlight.
Still, java fern does a lot better in these tanks.
I have to add I use peat granules instead of gravel or sand. Peat contains a lot of nutritious chemicals, so this probably influences their growth and tolerance of unfriendly waters.