Hexamita doesn't kill fish that quickly.
If the fish died shortly after you added the medication, you probably overdosed them.
Did you remove the rocks when you worked out the water volume?
Do you have any pictures of the dead fish?
Did they develop a cream/ white film over their body?
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You can wipe the inside of the tank and do a complete gravel clean and water change. Refill the tank with tap water (no dechlorinator needed).
Wash the filter under tap water and set it back up and get it running.
Add a heap of salt to the tank. Buy a bag of swimming pool salt and pour the whole bag in. Add so much salt it no longer dissolves and there is an inch of salt on the substrate. Let the tank run for a few days with the salt in and then drain and refill it a couple of times with fresh water. Then set the tank back up.
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You can sterilise rocks by putting them in the oven and cooking them at 100-150C for an hour.
If the fish died shortly after you added the medication, you probably overdosed them.
Did you remove the rocks when you worked out the water volume?
Do you have any pictures of the dead fish?
Did they develop a cream/ white film over their body?
------------------
You can wipe the inside of the tank and do a complete gravel clean and water change. Refill the tank with tap water (no dechlorinator needed).
Wash the filter under tap water and set it back up and get it running.
Add a heap of salt to the tank. Buy a bag of swimming pool salt and pour the whole bag in. Add so much salt it no longer dissolves and there is an inch of salt on the substrate. Let the tank run for a few days with the salt in and then drain and refill it a couple of times with fresh water. Then set the tank back up.
------------------
You can sterilise rocks by putting them in the oven and cooking them at 100-150C for an hour.