1 year old tank with sudden issues?!

[Erin B]

Hello,

I had a healthy tank until recently and am now confused as to what's going on.

Details:
50 gallon freshwater
Temp 78f
Fish: 9 neon tetras, 2 black mollies, I Dalmatian Molly, 1 Chinese Algae eater, 4 rose barn tetras and 2 male guppies.

I had a beautiful blue and red gouriami until about 2 months ago. I loved this fish and decided to replace him with a new gouriami along with 3 beautiful orange and black Lyra tail mollies.

I acclimatized these fish and then the next morning I saw my gouriami was dead (!) and I noticed the one of the new Lyra Mollies was hanging out near the top, resting on the back ledge of the heater. The other Lyra seemed to know something was up and was around it all the time. That one Lyra dies the next day and then the second Lyra started doing the same thing! The following day he was on the bottom dead too!!

Now As of today two of my neon tetras have died and one of my black mollies is laying on the bottom, on his belly, tail is bent a bit crooked and he is just hanging out there...what is going on in my tank?

I tested for nitrate and ammonia and it was zero. I typically do a 25% water change every 2-3 weeks and this has always been fine, until now when I introduced these new fish.

It doesn't look like ich either...but I do notice a bit of bloating in their bellies and aince they're males this is odd...

Suggestions??

 

[NeverFadeAway86]

not sure what is causing your issue but in the meantime may be a good idea to do more frequent water changes and see if that helps

 

[FreshyFresh]

A 25% water change every 2-3 weeks is not nearly enough. As a guess, this tank should have a minimum of a 50% weekly water change. I'd say that you have very high nitrates, which is slowly killing your fish.

The tank showing zero for nitrates can't be correct either. What test kit are you using?

 

[irishspy]

Yeah, my standard is a 20% change weekly. I agree with the suggestion above: you may want to do more frequent and larger changes for a while. Also, if your LFS will do water tests, take a sample of your tank water to them to double check your results. And good luck!

 

[tanker]

I think more then likely you introduced some pathogen into the tank.

 

[henningc]

I think the pathogen pushed already enviromentally stressed fish past the limit. I'd do a 50% water change and another 25% 2 days later. Then when the lights are off look at the fish with a flashlight. If you see the slime coat there are pathogens.