A year or two ago I bought a bag of Eco Complete with the intent on using it to replace the sand I have in a 10g. I never go around to that, and now I'm going to use it in a 20g long instead. I figured I would need a 2nd bag for that, so I just picked one up at PetCo, the last bag they had on the shelf. What caught my attention is that the liquid in the bag is a thick rust color, or maybe mustard, like a lot of iron is dissolved in it. The liquid in the old bag I have is clear. Is this rust color normal now for Eco Complete?

Bump: Sorry about the typo in the title. Should be "bag", not "big". I don't see how to fix it.

Wish I could help but I have never used it myself. I suspect that by the time you cycle the tank it will have remedied itself if there were a problem but just to be safe you could wait until they have more in the store and swap it out.

All the bags I have used (not a lot) have always been clear.
The liquid serves no purpose. I would rinse the old bag and refill with clear water. If that turns any color I think I would not use it in the tank. Perhaps rinse it out a lot more and see if it will stay clear.

I just bought some 3 months ago, and the eco-complete liquid was a dark brown color, It hasn't hurt my fish, so i believe it is normal, it also smells awful.

Did you rinse it first, or just dump it all in the tank, filled, and added fish?

Just dumped it, liquid and all

I returned it. Got a "normal" looking bag from another PetCo.

I got a reply from CaribSea today:

"Sounds like the bacteria are revved up in there. I would go ahead and give it a good rinse and then use it. Sometimes, maybe the heat, the spored bacteria come out of hibernation and start multiplying in the bag. It probably smells eggy too. It will be fine if you rinse it, the bacteria will never rinse away completely but you want to knock them back a bit. Sorry for the trouble!"

So good to know, but I've already returned it.