Join Date: Sep 2012
Location: Windsor, Ontario
Today, I got a definitive answer from Seachem in response to one of my posts in a forum they monitor.
Many members, including myself, will be relieved with this answer:
"I understand your confusion and apologize. The type of amine (tertiary, secondary, etc) is immaterial to the issue. It is the specific slime-coat chemical formulation of certain competing slime coat products that causes them to bond to polymer based resin materials in a manner that is highly resistant to oxidative destruction (via chlorine regeneration). If such a slime coat product had no amine as part of its chemical makeup the situation would merely be annoying, however the amine can undergo partial oxidation to a chloramine while still remaining bound to the resin via the slime coat material (likely through non-covalent interactions). It can then be slowly released back into the water through normal chemical breakdown of the slime coat material on the resin over time.
Although this phenomena exists with any polymer type resin (not just Purigen) it is particularly acute with Purigen because Purigen predominantly and selectively binds and removes amines (whereas other resins indiscriminately bind amines and other chemical groups). So the point is, it happens with all resins, but it happens more with Purigen. However it is not merely the fact that there is an amine present since Purigen removes a whole host of organic amine based nitrogenous waste and this is no issue at all since in those cases since those materials are readily oxidized and "burned" off the Purigen.
So, to answer your question, EDTA is not of concern in this situation as its overall structure is quite different from the amine based slime coat products (although we can't say what the differences are exactly since those other products are not ours and are proprietary). What we can say is we have never encountered this phenomena with EDTA based products nor have we encountered anecdotal evidence to suggest otherwise.
The prior tech support answer you received erred on the side of being overly cautious and was clouded I think by focusing on the amine aspect of this issue and not the slime coat aspect which is the actual source of the problem. I apologize for the confusion and we shall make sure all support staff here are on the same page with respect to this issue as well as updating our FAQ on this topic to add some clarity to this issue.."