I recently bought some fish from a fellow aquarist. they were 9 cardinal tetras, 2 corydoras and a flying fox. We bagged them up in one large fish bag, and I transported them about 4 miles. By the time I got them home the flying fox was dead, some of the tetras were dead, others were gasping and the corydoras's were ok. now the survivors are 2 tetra's and the corydoras. My question, what went wrong?...I havde transported many fish and have had them bagged for many hours with no losses. did I have too many fish in 1 bag? help....I do not want this to happen again..