So what fish have you got with your Chaetostoma milesi?
What size tank (dimensions please)?
What filtration and powerheads?
Having learnt the hard way with my first "Rubbernose" it is the first few weeks that should be the hardest in keeping this wonderful catfish, they are easily outcompeted for food and the process of starving them for transportation within the trade can send their system into shutdown (they simply lose the appetitie to eat). Quarantining for a month is ideal, which will enable the fish to get plenty of food and recover from the ordeal of being plucked from a Colombian river.
Some do readily adapt to hobby life, my one eats Tetra Prima and Hikari algae wafers, but then again I acquired my one from "MartinS" on here after he had owned it for several months. However, many need the "rock painting" trick to get them to eat, which involves finely crushing up a good mix of food and glueing it to a fist size pebble with egg white (which is left to go hard and dry out of water). You then simply have multiple pebbles and rotate which go in and out of the tank on a daily basis, presuming the catfish clears the pebble of food.
