Purigan - turns red

I've had that happen too. Not really sure why, except that the particular tank it was in had a thin layer of red cyano or another type of red algae on the rocks, which I blamed on the cheap, weak, and old PC lights on the tank. All other purigen I've used in both FW and SW has always turned dark brown and then bleached up nice.


Also just make sure you are following the post-bleach rinsing instructions. They used to recommend a low pH buffer soak afterwards to keep the Purigen from raising pH after re-introduction. That typically was not an issue (and not the process) for SW tank use. But I had a 100mL pouch running on a 10g FW planted livebreeder tank and after I recharged and soaked it per the directions it tanked the pH down to below 4 and killed everything. Seachem was good to work with, they were able to re-create the scenario in their labs and ended up changing the directions on the box because of it, so now it says to just rinse adequately. Partly my fault due to using 10x the amount that is recommended (100mL is for a 100g tank) but for FW planted I was using like 500mL on a 55g tank also because it doesn't strip the water like carbon does.


But the bottom line is after the bleach soak, I always rinse it very well then soak it in RODI and usually in a 5g bucket with a powerhead for several hours, then change the water and do it again.