Hooking up propane tank to gas log

I currently have a 50 gal propane tank which feeds a gas log in my fireplace. The tank is owned and serviced by a propane company. The gas log provides no heat for the house and is only for visual effect. I don't use the gas log much and don't want to pay the minimum usage charge to the propane company, so I'd like to get the tank removed and hook up a propane tank like the one on my BBQ grill.

Is there any reason that I can't use a gas grill tank & regulator with the right fitting attched to the copper line that feeds the gas log in my fireplace? Are there any dangers to be concerned with or recommendations on how to properly do this?

Some details: The tank is outside and there's a 3/8" (?) flexible copper line that comes in thru the basement and up to the fireplace. The gas log was there when we bought the house and I don't know the make/model and there's no owners manual. We vent through the fireplace damper.

Thanks,
Steve

Log

The design of the log's controls is what is most important. It MUST have a saftely pilot unit, not just light with a match. Where the gas comes from is immaterial as long as it has an approved gas line to the fireplace.