They get more confident as they get larger but still can frustrate for periods. Their behaviour can change and it doesn't always seem to make sense but persevere. I found feeding them at the same time helped encourage them. Blacking out the back and sides also. I lowered the flow to x5 and increased oxygenation via the venturi on my pumps. Dither fish, which I have, are supposed to help. It may take one to come out and the rest follow. I remember being frustrated with them but they have been great for around ten years now. My six are 28 years old. In between feeds I have one or two out foraging and others hiding. At feeding times they all come out enthusiastically for food and there is a lot or activity and competition so I spread the food out. This spectacle is great and on demand and I find it more interesting than all the fish being on display all the time.