My otos almost never come out

[16gallontanker]

Why is it my octos always hide in the tank and I almost never see them they all hide in the squidward decoration I've even tried putting a blanched cucumber in and they still don't come out. Is it because I only have 3

 

[Alice B]

How bright is your tank

 

[Colin_T]

They are nocturnal and prefer well planted tanks.