Q: When is Purigen®exhausted and how do I regenerate it?
A: Purigen will turn from its normal color to a deep brown when it is exhausted. Purigen can easily be regenerated by soaking it in a solution of hyperchlorite (generic) bleach overnight. The Purigen®will return to its original color. Then rinse well and dechlorinate using Prime®or Safe™to remove any chlorine. For freshwater, use a buffer to adjust the pH as needed due to bleach’s high pH.
Q: Will Purigen®reduce GH (general hardness; calcium/magnesium ion levels)? Is it meant to be a substitute for activated carbon or should it be used with carbon?
A: No, Purigen®will not impact calcium/magnesium hardness. It is superior to carbon in removing organics and not having negative impacts, but it is also compatible with carbon. The use of carbon with Purigen®will extend the useful life of Purigen.
Q: On some of the Purigen® documentation I have read it says that some slime coat products can contaminate Purigen® and render it toxic. Can you identify these products ?
A: Only certain slime coat products will cause Purigen® to become toxic; the products that do this are amine based. Prime® and Safe™ are not amine based and so will not cause this problem. If you're curious, what happens is that the amine compounds can strongly bind to the resin, then when they (the amines) come into contact with any chlorine they will form chloramines which are highly toxic. We offer a stress coat product, StressGuard™, which is not amine based and so can be used in conjunction with Purigen.™
Q: Does AP Stress Coat foul/ruin your Purigen product?
A: If they use an amine based polymer it will not foul the resin but will render it non-regenerable. What amine based polymers will do is bond not just to Purigen but to any organic scavenging resin as well as any ion exchange resin and when you attempt to regenerate the resin they will then bond with the chlorine to form chloramine which can be released into the aquarium. This is not just an issue with Purigen but with all resins being sold in the pet trade. The problem only occurs when one attempts to regenerate the resin, there is no problem unless you wish to regenerate the resin you are using. Seachem products do not contain amine based polymers and are safe to be used in conjunction with not only our resins but also with other companies resins.
Q: If a product contains EDTA, and since EDTA is amine based, will such products cause the same regeneration issues with Purigen as occur with amine based slime coat products?
A: 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.