I presume you mean pimafix and melafix?
Pimafix contains clove oil which is often used to euthanise fish. You have to be careful not to overdose.
These are commonly used medications and generally dont cause adverse reactions if used correctly. They also arent very likely to be beneficial as they are nothing more than herbal remedies.
I would look more into why the fish had damaged fins as being the cause of death rather than just assume it was the medication.
Do you have any pictures of the dead guppies?
How long did you have the guppies for before adding the medication to the tank?
Have you added anything to the tank in the 2 weeks before this happened?
What is the ammonia, nitrite, nitrate and pH of the aquarium water?
How long has the tank been set up for?
Do you have any pictures of the dead guppies?
How long did you have the guppies for before adding the medication to the tank?
Have you added anything to the tank in the 2 weeks before this happened?
What is the ammonia, nitrite, nitrate and pH of the aquarium water?
How long has the tank been set up for?
I do not have pics of the dead guppies. I placed in the trash, the dead guppies.
I did not know what else to do with the dead fish.
You don't want to replace cartridges unless they start to fall apart. Then you replace them with sponge for a different brand of filter. Sponges last a lot longer and can be cleaned in a bucket of tank water and the sponge gets re-used.
You can add sponges to the filter now and in a few months remove one of the old cartridges.
The cartridges/ sponges hold good bacteria that help keep the water clean. So you only replace them when they start to fall apart.
To clean the filter media (sponges, cartridges), you squeeze them out in a bucket of aquarium water. The media gets re-used in the filter and the bucket of dirty water gets poured on the lawn.
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If the guppies are being nipped by the tetras, then move them to the 6 gallon tank. Just make sure they have a filter and don't feed them too much. And do regular water changes to keep the tank clean.
I would say 3 male guppies is maximum for the 6 gallon tank. They have small territories and need their space so you don't want too many otherwise they could fight. Smaller tanks also have more issues with the water quality deteriorating, so the fewer fish the better the water quality.
Aquarium heaters range in wattages and it depends on how cold the room and house get in winter. If the room the tank is located in stays warm in winter, a smaller heater (50 watt) is probably sufficient for the 6 gallon tank. If the room gets cold, then a 75 or 100 watt heater would be better.
For some reason the 50 and 75 watt heaters aren't as reliable as the 100 watt heaters so look for a reasonable brand with a good warranty. If you plan on getting a bigger tank in the future, go for the 100 watt heater and it can be used in a tank up to 10-15 gallons.
Use a thermometer that sits in the water to monitor the temperature.