The long tubes are usually fine. The regular 10.0 ones must be mounted around 12" from the tortoise to get UV benefit. The HO units can be mounted a bit farther away at 18+".
Is there such thing as to leaving it on too long? I'll turn it on before work and I don't get home til about 14 hours later is that ok. I've noticed the tortoise sometimes scratches its eyes also sometimes it opens its left eye and it takes it a while for the right eye to open. Any input would be appreciated. Thanks for your advise.
What bulb are you currently using? Eye scratching can sometimes be caused by lights.
You can certainly leave it on for too long - 24 hours a day, for instance, would be way too long, but 12-14 hours is standard. If you're concerned, just buy a timer so you don't have to worry about turning it on and off. Most keepers use timers for their lights.
I have mine on a timer for 14 hours a day. Are you using a smaller coil shaped bulb or a long one.? The compact fluorescent bulbs have been known to cause I issues for tortoises. Also if your substrate is dry and dusty that can irritate their eyes. How far away from the top of your tortoise is your bulb?
I have a 18 inch tube style uv bulb 10.0 ho about 18 inches above the the tank. Have cypress mulch and some grass in his habitat. I thought I had read on here that basking lights sometimes can also hurt their eyes but can't find it anymore.