Help!!! My fish are dying!!!

I have a tank emergency my fish are dying in my community tank. Water parameters are all great, but fish swimming in the corner near surface. I added a new bubble bar and replaced air pump two days ago in case it was oxygen levels. Lost a dojo loach earlier in the week and angel fish today. Fish store recommended I treat with seachem paragard. About an hour after I treated tank my large pictus catfish died (he had been acting fine) and about 10 more fish were at the surface close to death (I lost a Cory and Molly since the catfish about an hour ago). My other molly had ichish spots appear this evening (after treatment). I called the fish store who recommended adding carbon filter back and doing a 25% water change. Now everyone who is left is swimming better and the ichish spots have disappeared (I’ll attach pic from when the spots showed up). Any idea what is going on? Is it ich and I need to re-treat with a different chemical tomorrow? Help!

How big is your tank? Have you added any new plants/fish recently?

HoldenOn said:

How big is your tank? Have you added any new plants/fish recently?

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A 45 gallon aquarium. Yes I recently added mollies and dojo loaches as well as a java fern.

I won't comment on disease because I really don't know enough. Perhaps @AdoraBelle Dearheart and @essjay can help though!

HoldenOn said:

I won't comment on disease because I really don't know enough. Perhaps @AdoraBelle Dearheart and @essjay can help though!

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Thank you!!!

Did any of the fish show physical symptoms?
What exactly are the readings for ammonia, nitrite and nitrate?
Could any contaminant have got in the tank - aerosols, paint fumes, someone cleaned the tank with a chemical, any hand cream or perfume on your hands when you put them in the tank?
How big is the tank and what fish do you have (both those left and those which died)?
What is your usual maintenance regime?


Do a big water change, around 75%, and run carbon which will remove any contaminant and the paraguard.

It is possible that the new fish brought a disease into the tank but without physical symptoms it is hard to say what.
Gasping at the top usually means something not right with the water, from ammonia/nitrite to something that has got in the tank.

Thank you essjay! My tank is 45 gallons and I have been doing water changes about 2-3 times per week. My nitrates, nitrites, and ammonia show zero...ph is in the 7 range. We had gone years without introducing new fish and were down to just the pictus catfish until about 3 weeks ago. We added one troupe of fish at a time and waited a few days in between but I feel pretty sure we brought something home with the fish. What has died in the past few days has been an angel fish, a dojo loach, my pictus catfish. and a molly. The paragard is the only chemical....except I did clean the filter housing with a white vinegar solution. What I have left currently are a couple of mollies, couple of dojo, couple of cories, one golden killie, couple of clown loaches, a bristle nose pleco, and 3 Siamese algae eaters. I’ll do a big water change today like you suggested. Symptoms are the fish swimming funny and the spots that come and go.

Did you make sure all the vinegar was completely removed after you used it on the filter housing?

essjay said:

Did you make sure all the vinegar was completely removed after you used it on the filter housing?

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I rinsed it, but I may not have rinsed it well enough...

As a matter of interest, why did you use vinegar? I am paranoid about getting things in my tank so I usually use a toothbrush or a pan scrubber (the kind with no detergent). Was there something on the casing that wouldn't come off?

We have a lot of lime and minerals in our water so it gets this really crusty white layer from evaporation....I let it soak in the vinegar solution for 24 hours until it loosened enough to scrape clean. Then rinsed.
My husband ended up having a major strep infection this summer that caused him to need open heart surgery so I had about 3 months of craziness where I neglected my tanks....I had just gotten them all back up to perfect water conditions before I started replacing fish. Just a rough summer for us.

Vinegar works well on limescale.


I'm sorry to hear about your husband, I hope he is on the mend now.