My fish are dying!

[Budden]

i have had my fish for over a year now. Quite recently I bought 5 new gourami's and within a week they were all dead. Since I did a water change and tested the water which was fine. Now my Bolevian rams have got a dark Black colour and my red rainbow has gone silver.

They are eating, and I really have no idea why they dont look well.
I called the place where I got the gouramis and they phoned the supplier. THey said they havent had any other problems.

Does anyone know what it could be?

 

[Terrorbyte]

i have had my fish for over a year now. Quite recently I bought 5 new gourami's and within a week they were all dead. Since I did a water change and tested the water which was fine. Now my Bolevian rams have got a dark Black colour and my red rainbow has gone silver.

They are eating, and I really have no idea why they dont look well.
I called the place where I got the gouramis and they phoned the supplier. THey said they havent had any other problems.

Does anyone know what it could be?

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Have you tested your water for ammonia/nitrites/nitrates? Fish should also be added gradually, especially gouramis (as many species of gouramis are not considered small, schooling fish). Adding 5 fish all at once may have spiked your ammonia to dangerous levels, killing off the gouramis, which were most likely already stressed, being in a new tank and environment. Even in an established tank, fish need to be added slowly so that the nitrifying bacteria colonies can adjust accordingly to handle the increased ammonia discharge from the fish.

How large is your tank? How often do you change your water, and how much do you change? What type of filtration are you using?

 

[WILDER]

I agree could of gone into a mini cycle, can you post water stats in ammonia,nitrite,nitrate,and ph, how many gallons is the tank, plus how many fish and which type.