fish loss

Question
i have a 55gal tank
i just tried breeder fish 5X
then i tried danios %X 2nd time around
i normaly leave them in the bag for around 10mins - 20mins in the bag to aclimatise to the water
my temp is around 75 in the tank i have not changed anything from when it was running good to now apart from the water was left for about a month with the filter and air stones running but with the fish and i added cycle to this during that month?
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Followup To

Question -
"I had my tank set up nicely and had around 20 neons gouramie mollys just
community fish... Well i moved my fish tank with more than a 50% water change
all my fish unfortunatly floated. Then i left my tank still for around a month
or so and now have started again PH is 7.2 amonnia,nitrate,nitrite is superb
alkalinitly and hardness is great but my fish last less than a day. ?
everything says my water is great ?"

Answer -
Hi Matt;

Replacing so much water at once probably shocked them. The water chemistry was just enough different that the fish couldn't tolerate it. If you have been adding new ones again and those have died, something else is going on. Let's see if we can figure it out....

What size is the tank?
What kinds of new fish have you tried lately?
How many new ones have you added at a time?
What acclimation method do you usually use?
How long are your new fish in the bags from the time they leave the fish store tanks to the time they are released into your tank?
What is the water temperature in the tank?

Let me know, as well as anything else that comes to mind about your fish and your tank.......

At Your Service;
Chris Robbins

Answer
Hi Matt;

Hmmm. Weird. The tank is plenty big enough and there really weren't too many fish added as long as they were all an inch or smaller. I can't think of anything else that would be a factor. The product called "cycle" is just fine to use but it really doesn't do anything. I have tried it many times and spent a lot of money testing it out. It did very little to nothing in my tanks. The only product I know for sure that works, as long as it is kept refrigerated properly, is called "Bio-Spira". It works because the bacteria colonies are kept in cool preservation. These colonies cannot survive being in a bottle on a shelf. That's why the others don't work.

You might consider draining the tank and refilling. Perhaps something toxic accidently came into contact with your equipment and it's still in there? Soap, detergent, cleaners, etc., can all cause sudden death. Even air fresheners, hairsprays, bug spray, spray lubricants, etc., can all find their way into there. A container used to add water to the tank that came into contact accidently with anything? Even just a plastic bucket that was used to hold floor cleaner and a mop with can be a problem. No amount of rinsing a plastic bucket is enough with that kind of thing having ever been in there.

Drain the whole tank while vacuuming the gravel and replace the carbon and/or zeolite portions of your filters (zeo looks like white or yellowish carbon). They will filter stuff out but can also re-release it to the water once they become filled. It is best to use them only for a week or so and remove them. Replace with the same type of media or put a more permanent one in it's place. I don't even use carbon and zeo anymore unless I need to remove remnants of medication or coloration from driftwood. I remove it in a week or so to prevent re-release of toxins.

I hope it works for you......