On Monday, September 21, I started using Melafix and Pimafix. I have a 15 gallon freshwater tank that holds 12 gallons.

I think two days ago I medicated the tank twice. I put a teaspoon of Melafix and Pimafix in the tank during the afternoon. During the night I put the same amount in the tank.

One of my fish which already looked like something was wrong with it before the treatment, died yesterday. Today there was a fish that was hiding behind the filter. I unplugged the filter and the fish came out from behind.

It later tried to jump out of the water and it got stuck inside the tank on the glass, between the area where the water and the top of the tank is. I pushed it back in.

It was having trouble swimming. Later it died.

For the next treatment should I use less? If so how much should I use and for how long? This is a seven day treatment and this is my fifth day. Both medicines say to use 1 teaspoon for every ten gallons of aquarium water.
I am treating them for tailrot.
I siphoned out six gallons of fish water this Sunday. Then on Monday I decided to keep three gallons of water so it will have the beneficial bacteria in it, so I took out three gallons from the tank and added three gallons of fresh water in the tank after I put stress coat in the three gallons I put in the tank.
I am keeping the water I took out to put the fish in goldfish bowls because I am cleaning out the whole tank due to overcrowding after treatment.
I will put a biological booster after cleaning out the whole tank in the tank.
Anyway I wonder if the first fish died because of the three more gallons taken out on Monday.
I know both meds can be used together because Pimafix says it can be used with Melafix.
I did remove the cartridge from the filter like the instructions say.
I also know the tailrot is from bacteria due to overcrowding because the tails have rotted jagged and I read about it on a website. These meds treat for bacteria you guys.