2 weeks ago I bought 100 pcs neon treta and placed them in my 3 ft tank. All healty and growing. Last week, I bought 20 pcs of guppies. Within a few hours, they were grasping for breath and within 3 days 12 of them died. They stay on top of the tank most of the time and appear lethagic. One of the female even gave birth. Today 4 pcs left after somemore died. Even the a few of the fries died after growing for about 4 days. Yes I noticed the fries really grow, but died in no time. All 100 pcs of my neon tetra no problem. Can anyone help?