Harlequin Rasbora Dying One By One

[Mumi]

I just bought 5 harlequin rasbora for my new aquarium 3 days ago at petco. They seemed happy and were very active, and ate well. Two died today. The first to die had two tiny white specs on his fins, so I thought it might be ick and immediately started introducing a low concentration of aquarium salt to the tank over the day (1 tbs for 6 gallons). The second to die had no visible signs of illness. One hour before I found it dead it was swimming and playing in the filter flow of water with no signs of problems.

As background: I have a 6 gallon fluval edge tank, with gravel and plastic plants only so far. I left the tank with heated water (treated with topfin quick start and stress coat water conditioner) for a week before adding the new fish to it, and left their bag floating in the tank for a while to acclimate them before introducing them. There are only the 3 harlequins still alive in the tank.

What could be wrong with my fish? And was adding aquarium salt a bad idea? Any input is appreciated, I really don't want any more of my fish to die.

 

[PrairieSunflower]

Welcome to the forum.
 
To start, you need to do a large water change with dechlorinated and temperature matched water.
 
You are currently in the middle of a fish in cycle (a filter needs to be cycled in order to handle processing the ammonia that fish produce... this process takes several weeks)... in the meantime, your fish are producing harmful levels of ammonia which will weaken their immune system and kill them.
 
Please visit the beginner's section for advice on how to handle a fish in cycle.  The short of it is, you will need to invest in a test kit to test your water so you can know the levels of ammonia (which should always be 0), nitrite (also should be zero)... and nitrate (which should grow, but 10 is a normal/average reading... higher isn't necessarily bad).  You will need to do daily LARGE water changes to keep your ammonia at 0 for the safety of your fish until your test results show that your filter is processing the ammonia and then the frequency of your water changes can drop back.

 

[Mumi]

Thank you so much! I am kicking myself for being impatient to get my fish; though I thought a week was long enough to cycle. One thing I didn't see in the beginners section is how long it takes to cycle with fish in the tank?

Also, after reading your post I added and "emergency dose" of water conditioner in hopes of removing the ammonia ASAP to get them through the night, and am doing a water change this morning. This seems to have worked, but is it a good idea to continue putting extra water conditioner on the water with water changes? Getting my testing kit today. I assume I don't want ammonia to be zero right away cause the filter bacteria need food to grow, but how high is dangerous?

Thanks again for your input! I have had a betta fish bowl for many years and am ace with taking care of them (which led me to think I knew what I was doing with a larger fish tank) but new to having a filter tank.

 

[PrairieSunflower]

It is a common mistake and so very frustrating, I think you will find a high percentage of us all started off the same way with fish.  The best tip is... don't trust people who work in fish shops... it is rare you find one that gives you excellent or accurate advice.
 
I don't know the length of time for fish in cycling as I've not done it that way myself and I am sure it can vary a lot.  You are right that your filter needs ammonia to grow bacteria, but at the same time your fish need you to be keeping their water levels of ammonia at 0.  So, I do believe the process will take longer since you have to consider the health and safety of your fish.

There are ways you can jumpstart the process, such as see if you can buy some mature media from the fish shop (media is what the bacteria grows on, such as the sponge in your filter).  If you can buy some and put it in your filter (the more the better) that will add a colony of bacteria for you to grow.... keep it wet in transport).
 
If you ever need to clean your filter sponges (because they have become full of gunk and the water flow has dropped), take old tank water from your tank into another container and squeeze your sponges clean in that water. This will make sure you don't clean the good bacteria away as tap water can kill the bacteria.
 
You shouldn't need to add extra dechlorinator to your water during water changes (or between).  A regular dosage as per your bottle is fine.  If you are getting ammonia a water change is what you need to rectify the problem (always dechlorinated and temperature matched).
 
As you have also mentioned that your fish seems to have ich, I'd suggest also posting in the emergency section and link to this thread as well so people can know what you are dealing with having a new tank.  While I know how to treat ich, I'm not confident on the precedure you should follow while also dealing with a new tank that needs frequent water changes.