I feed my L140 hikari algae wafers, the occasional JBL novo tab and courgette.
I use shrimp pellets and novo tab as a staple diet for my L270.
You can also use wardley algae wafers for the L140.
In terms of confidence building, having lots of hiding spaces available helps.
I feed mine 1-3 times a day, but only small amounts. Sometimes I wont feed them.
I find a small night time feeding is more accepted than day time ones with my L140. But they should take food that your other fish don't eat