Light - how low can you go?

[oreo57]

Dear Annie,
please excuse my post above. a.)Since the system ran accidentially without artificial light now for 9 weeks, it is not an adequate reaction to your initial question. b.) i wont proceed the experiment, because sunlight has no too much decreased, if at all an hour or so, and also i want to be able to stare into the tank when i come home after work.

What i can contribute is the observation of slight growth and not stagnation, on eleocharis mini, juncus repens, helanthium tenellum, lilaeopsis and frogbit, during the two months without artificial light. (+CO2 injection and some tabs in the sand)

You may be surprised at the amount of light is in that indirect light.
currently my 55 has 1535 Lux (est 35 par) hitting it from indirect sunlight.

Tank looks dark.

Just use a phone app for lux and divide reading by 43.5 for daylight