To my surprise I came home today after a 5 days vacation and I realized that the timer was set to ALWAYS ON. The fish all look ok. The plants are covered in algae. How harmful was that to the fish? Is there a way to recover the plants? Gosh I am so stupid
I've done that before. In fact, I've done both, leaving lights on and leaving lights off while away. It's not detrimental to the fish.
Your plants will recover and the algae will decrease as you're back to your regular lighting schedule. If necessary, you could do a shorter "lights on" period while you are dealing with excess algae. Don't worry!
I wouldn't leave them off that long simply because you DO have plants. I would just cut back by a few hours of light per day. It will be a gradual thing to get rid of the algae. Kind of like losing weight.