Help!

[SombreroBanana]

I've had something ravaging my zebra danio tank for the last week or so, and it's wiped out 5 of the 7 in the last few days. I made these two posts a few days ago: http/www.fishforums.net/index.php?/topic/410466-possible-mouthrot/ - http/www.fishforums.net/index.php?/topic/410476-zebra-danio-with-parasite/. Basically 4 of the five started not closing their mouths and swimming only at the top, then they died. One of the five lost all the color in its back half, and couldn't swim so it basically couldn't get water through its gills. What's going on? I'm wanting to get more fish, but if they're just gonna die I'd rather wait and go through some medication. Please help!

 

[MrsM]

what are your water test results for ammonia, nitrite and nitrate?
how long have you had the tank running?
what size is the tank?

 

[SombreroBanana]

Ammonia 0, nitrite 0, nitrate 40 (it was around 10 when they started dying off, I'm about to do water changes now).
It's fully cycled. I got the fish on Wednesday.
20 gallon long aquarium.

 

[MrsM]

just read on your other thread that the fish died? sorry for your loss, best to keep 1 thread per problem though, stops confusion... :

 

[SombreroBanana]

just read on your other thread that the fish died?

sorry for your loss, best to keep 1 thread per problem though, stops confusion...

:

Yeah, I originally posted in those again when they kept dying because nobody really gave me a straight answer, but nobody responded so I decided I'd post here.

 

[MrsM]

hope your next fish live long and healthy, best to get some new fish before the "good" bacteria in your filter dies off though, remember to acclimate fish slowly... good luck

oh and it sounds like it could have been parasitic worms...but i couldnt be sure..