just wondering..

It is not (just) excess nutrients that cause the algae. It is specifically an imbalance of nutrients and light. It can also be light coming in from a window and hitting the glass. Try playing with the amount of time the lights are on for at least a week at a time and find the sweet spot.

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Really, I call that a trick question. Cause it miss leads the person into what can only be speculation.
On the other hand, I never got algae in water that I put it in the closet and left it for months at a time even though it had lots of nutrients in it.
Light...and usually in long periods of time per day are needed in most cases to cause
algae. But after formed some kinds seem to hang on days or weeks after the light has been taken away.
And BTW in most any naturally occurring water algae exist except perhaps underground streams may be free of it. It's a plant and needs light AND nutrients to grow.