community tank was set up about five years ago and stocked with 2 guppy pairs and 2 albino corys. Fast forward to last Sunday, took the kids to the beach and brought back some seaweed and put it in the tank. Next morning, about 15 of 20 or so guppies are dead and the corys are looking stressed...removed the seaweed, set up a 10 gal
tank with tap water and transferred whoever was alive. The rest were dead by afternoon, even the corys. Don't know the seaweed species, but it was red/brown with small float sacs, not kelp, more frilly like Sargasso. I've put seaweed in this tank for for years from the same beach in San Diego with no problems, so this was a shock. Concern now is was the seaweed toxic, or did this come from Fukishima since the kill was so quick. Any ideas?