Cleaned Established Tank And 3 Of My Fish Died

[Stormer]

I have a 10 gallon, cycled tank that has been up and running for almost a year with the same 5 fish but then I decided to get a new air pump since the aeration was not the best.   I also decided to redo the tank (I now know not a brilliant idea) and bought new gravel (rinsed several times before adding).   I left 1/2 of the old gravel in the aquarium and cleaned the tank before adding the new gravel.  I put the filter media in the old tank water while doing so.  I emptied the tank about 80% and then used Prime to refill my tank, just like I've done in the past.   I hooked everything back up and let the aquarium run for about an hour and then added my 5 fish.   4 hours later I had 3 dead fish.   I checked the water with my API master test kit and my ammonia was .50 which is what I have in my tap and my nitrites were 0 and my nitrates were 5-10.    This morning I get up to my tank being cloudy.  I checked the water again and I now have .25 ammonia and 0 nitrites.  I did not check the nitrates.   I can only assume I cleaned my tank too much and have some type of imbalance.   I have moved my remaining 2 fish over to my hospital tank.   
 
What should I do with my tank?   Do I need to do water changes?   Do I need to start the cycle process all over again?   I'm at a loss and don't want to put my fish back in until I know they will be safe as I've had them for almost 1 year.
 
Stormer

 

[Far_King]

If I was to change the substrate in the tank I'd not clean the rest of the tank and certainly wouldn't touch the filter.  I think sadly what has happened is the tank has crashed and is now cycling again.  If you can keep them in the hospital tank until the main tank is cycled that would be preferable.

 

[Ch4rlie]

Oh dear, sorry for your losses first of all.
 
It does sound like a case of overcleaning and inadvertently reducing your bacteria colony numbers. bacteria lives ALL over your tank, subtrate, glass, plants, decor etc and as well as inside the filter, so by swapping half your gravel over alone, you would be getting rid of a good number of bacteria, so cleaning the glass and the filter as well is going to undoubtly leave too small a colony of bacteria to deal with your ammonia and nitrite levels.
 
Getting 0.5ppm of ammonia straight from the tap does not help matters at all.
 
You have a choice, keep your fish in the hospital tank as Far_King suggests until main tank is cycled fully or keep in main tank, not a huge amount of difference either way imho since both would need water changes and monitoring of water tests etc.
 
The only concern is how fast that killed your fish when you returned them back to the tank, usually ammonia / nitrite will take longer to kill them, but of course there are variables in this.
 
But personally I would still keep them in the main tank and advise to change the water to reduce ammonia as much as you can and not forgetting to add the dechlorinator.
 
I should think it won't take too long before your bacteria numbers getting back to strength since you still have the filter media with bacs.
 
Continue with testing your water and changing water when you see symptoms and/or ammonia/nitrite levels being too high and hopefully in a week or less you may be back to normal.

 

[Stormer]

So I don't need to start all over with the cycling process and instead just do water changes?   It just worries me to put the fish back in not knowing if my cycle has just stopped or it is just recovering.   I now know better for next time not to go overboard with cleaning.   
 
Do I just do water changes when I see a reading of ammonia and nitrites?    Sorry, I took me 30 days to do a fishless cycle so I understand that part of it but this is all new to me.

 

[Far_King]

Regardless which approach you take the tank is cycling again.
 
Charlie has suggested you cycle with the remaining fish as you no doubt have a colony of bacteria even though they are small.  Water changes will reduce the ammonia during the cycling and the bacteria will grow to deal with the waste from the remaining fish.

The difficulty is the amount of ammonia that's in your tap water and that's probably increased the load on the bacteria that remained in the filter.

 

[Stormer]

I decided to go the fishless route since my remaining fish are happy in my spare tank I put them in and I didn't want to risk them dying as well.   I do have some issues though.  
 
I started the fishless cycle once again since nothing was happening since it seemed like I had wiped out most of the bacteria.  Changed out most of the water then added pure ammonia to 2.50 (I have .50 in my tap).  The ammonia started to go down after 2 days but no nitrites ever and nitrates are not going up either.
 
March 11th:   Ammonia:  2ppm
                      Nitrite:  0 ppm
March 12th:   Ammonia:  2 ppm
 
March 13th:  Ammonia:  1.50 ppm
                     Nitrite:  0 ppm
March 14th:  Ammonia:  .50 ppm
                     Nitrite:  0 ppm
March 15th:  ammonia:  .25 ppm
                     Nitrite:  0 ppm
March 16th:  Ammonia:  .25 ppm
                     Nitrite:  0 ppm
 
 
 
 
The rest of the water is:   PH: 7.8 and Nitrates are at 5 ppm and holding
 
 
 
At this point I am stumped and have no clue where I am in the cycle and what my next step should be, any help would be appreciated.   It took the tank 31 days to fishless cycle last May from start to finish.   
 
10 gallon tank
Aquaclear 20 filter
Bubbler
Heater set at 84 degrees
Prime declorinator
No live plants
Gravel
No fish in tank currently