My fish are dying, is it because I upset the bio-filter?

Question

80 galon aquarium with 3 filters, one cannister filter, one powerhead, and one waterfall... I changed the filter media at the same time for the powerhead and the waterfall. Could that be sufficient to cause them to die? I assumed the cannister filter provided the bulk of the biofilter. was i wrong?

Answer 1

It depends on the O2 levels in you canister,if the flow of well oxygenated water gets used up before reaching the bio-filter section of the canister it's possible that the other two filters were carrying the load. Are you experiencing elevated Ammonia or Nitrite levels? If so this is probably the answer. If not,then you have to look elsewhere for a culprit.