Is iv saline a good treatment for pots?

Initially, yes: If POTS is due to dehydration, or if dehydration is contributing to blood pressure instability, then IV saline is a good starting point. However, if symptoms persist despite adequate (re-)hydration, then you have to look to medications - Florinef, (fludrocortisone) Midodrine - and other interventions (compression hose - it's actually the most effective in controlling POTS symptoms but people don't like to wear them