Okay I will get a sword tomorrow. Should a wait longer to add any Cory's to my tank. Or can I add them with the sword.
It has now been five or six days since the last fish deaths (your post of April 17). The two guppies look OK in the video; if they are still behaving normally, with no sign of trouble, you should be OK to add a few fish. Corys are highly sensitive to almost everything, so give them a very good look-over in the store tank to ensure they are "normal" in behaviours, at least as normal as one might expect from corys in a less-than-desirable environment like the store tank. You want no fewer than five corys, so 5-6, acquired together (they will settle in much better this way).
Byron.