Kuhlis will live up to 10+ years, and grow more slowly as they age. As everyone else mentioned, the more hidey holes, the better. Caves, PVC pipes, decor, rocks, rocky cave formations, under broad leafed plants,
in plants, under catappa almond leaves, and under driftwood.
From description, they sound like juveniles. They will be shy, and won't venture out up to 2+ weeks. They will usually be more active during the night, but can be taught to come out during the day.
Avoid bright lights, or even better, if you have bright lights, get moonlights and a timer. Set the moonlights to come on about 5-10 minutes before the main lights. This will give them a chance to adjust to the light and not be spooked by a sudden burst of light.
What other fish are in the tank, how big, and is there sand?
You will enjoy these little guys so much, I absolutely love them. They will always surprise you, and each kuhli has its own personality. It's even more fun to learn to identify them and give them names. I have 5, and I can tell them all aprt. They are Leo, Lily, Luke, Luna, and Lorelei
Try feeding them protein rich foods. They will enjoy them, and it will help them grow. Frozen bloodworms, brineshrimp, mysis shrimp, and tubifex worms will be good. As well as a good staple food. They also simply adore cooked peas. They go absolutely bonkers
http/www.youtube.com/watch?v=vHsyBCtNVso&list=UU7s40nMnAGlQukUspscHIRA&index=2&feature=plcp