I keep all my tube nems in either PVC pipes or bottle (just make sure there is an opening at the end so they can grow) since I have a bare bottom. This way I can move them as needed as they grow. Their sting has killed a frogspawn, almost killed a BTA, and wiped out a large Hollywood stunner chalice...
Your tank looks very unique with those tube nems, I don’t see many around. How do they go with fish?