Never used it. From personal experience, I've used the following:
- API StressCoat+ : Use this on my daughters 5G tank. Works well, but can't regen the Purigen with it.
- SeaChem Prime: Expensive, but you use so little (it's uber concentrated) that a bottle will last for months. I just finished a 250mL bottle that I bought in July. I use this exclusively on my 56 gallon tank, and use it to regen the Purigen I run in the tanks.