Originally Posted by txaggie08

PLEASE read the HPA Q&A sticky so we don't have to answer the questions about the difference.

HPA is highly recommended on the ion, and if CO2 is used an anti-siphon tank is nearly mandatory. The use of a CO2 oriented reg like a palmer stab is also recommended.

Please use the search button and read the stickies first next time, this has been discussed ad-naseum and the answers to your questions are all in this forum...