Quick question on lighting..

[Heisenberg]

I have a 30g with 6 tiger barbs, 2 platys, and a few neons established for 9 months, light on 24 hours. I have a 20 g with 4 ruby barbs, 3 golden danios, and 1 golden algae eater established for 7 weeks. I read that it is beneficial to cut the light off at night to mock nature so I have done this with the new tank since day one. Will it stress the fish enough to harm them if I start turning the light off on the 30g since they have had it on for 9 months?
Thanks in advance

 

[tomtom14]

No it should be beneficial if they have had no dark for 9months.

 

[Heisenberg]

No it should be beneficial if they have had no dark for 9months.

Thank you