We are not new to freshwater aquariums, but the problem I am having is very new to me. I recently got rid of my 15 year old 80 gallon Oceanic tank and replaced it with a new bow front 45 gallon which fits better in our new house. Same wet dry filter, ornaments, etc. New tank and rocks. Broke down the 80, set up the 45, moved the wet dry filter hoping to maintain the years of good bacteria moved the fish and within 2 weeks everything was dead. I have tested for ammonia and everything shows good. Standard Amquel water, etc. After it all died I did a partial 50% water change and waited 2 weeks just filtering the water with no fish. Today I added 6 fish to the tank and within 5 hours all were dead. Does anyone have any ideas??? Help!!!