How long have you had the fish for?
Have you added anything to the aquarium in the 2 weeks before this started?
What did you do to the tank on the day before they started dying?
How long have they been dying for?
What symptoms do the fish have before and after death?
Pictures and video of the fish so we can check them for diseases?
Picture showing the entire aquarium so we can see how it's set out?
What have you treated them with?
What are you using to deworm them and how long have you been deworming them?
How long has the tank been set up for?
What are the tank dimensions (length x width x height)?
How big are the fish?
What other fishes are in the tank?
What is the water temperature?
What is the GH and KH of the water?
Is there lots of aeration/ surface turbulence in the tank?
What do you feed the fish and how often do you feed them?
What is the ammonia, nitrite, nitrate and pH in numbers?
What sort of filter is on the aquarium?
How often and how do you clean the filter?
How often do you do water changes and how much do you change?
Do you gravel clean the substrate when you do a water change?
Do you dechlorinate the new water before adding it to the aquarium?
Do you have buckets used for the fish tanks only or do you use any buckets around the house.