Sick fish

[Pete P]

I have had a 50 gal. Tank for 3 years, I started with three goldfish then added a bristle nose pleco. A few weeks ago we decided to add some fish so we settled on 8 giant danios (1 1/2”) I quarantined the danios for a week in a separate tank and then added them to the 50 gal. All seemed well for about a week when the goldfish started to hang out ate the bottom. I decided to treat the tank with API general cure as a precaution, did my weekly water change, all tests were perfect, this week the pleco started coming out during the day which it seldom did. The goldfish looked worse. Yesterday the pleco and a goldfish died and the last 2 look like they won’t make it much longer. I retested the water and it couldn’t be any better. I have notice what looks like white fuzz growing on some fake plants. ???????..what’s wrong….?

Pete

 

[Andy Sager]

I have had a 50 gal. Tank for 3 years, I started with three goldfish then added a bristle nose pleco. A few weeks ago we decided to add some fish so we settled on 8 giant danios (1 1/2”) I quarantined the danios for a week in a separate tank and then added them to the 50 gal. All seemed well for about a week when the goldfish started to hang out ate the bottom. I decided to treat the tank with API general cure as a precaution, did my weekly water change, all tests were perfect, this week the pleco started coming out during the day which it seldom did. The goldfish looked worse. Yesterday the pleco and a goldfish died and the last 2 look like they won’t make it much longer. I retested the water and it couldn’t be any better. I have notice what looks like white fuzz growing on some fake plants. ???????..what’s wrong….?

Pete

A couple of things:
First off, plecos and goldfish are not a good combination. Oftentimes plecos will scrape the slime off goldfish which is not good for the pleco or the goldfish.
Second, 1 week is not nearly enough time to quarantine any fish. Fish can carry parasites that have lifecycles as long as 90-100 days so quarantining for anything less than that opens you to potential problems. I made this post to explain the differences and uses of Quarantine and Hospital tanks that may help you: Quarantine tanks and Hospital tanks, are they really different?

How long after the introduction of the Danios did the fish start not doing well?
What are you feeding all the fish?
Next, API's General cure is a bit misleading in name. It's not an all in one medication to treat everything. It treats specific things but not everything. Without knowing what you were treating for, that medication may have done nothing for the fish. We'd need to know you water parameter numbers to recommend something different if appropriate.
A 50 gallon tank is not really the best for goldfish. What kind of goldfish did you have and what is the dimensions of the aquarium?
If you can post pictures of the the fuzz on the plants and the current fish that are alive, it may help better diagnose a problem. If still shots are too tough, take a 1 minute video of the fish and tank and post it to Youtube or similar type program and post the link to the video here.
Let's start there.

 

[Pete P]

Thanks for responding to my message. I don’t think the pleco and goldfish were an issue as the have been together for 3 years without any issues. Since writing this post yesterday I have lost the remaining goldfish and two danios. I think you are correct that I did not quarantine the danios long enough. I suspect the remaining danios will follow soon. The fuzz seams to have cleared up. I have retested the water again and it can’t get much better. My plan at this point is to let the tank cycle for a couple of months and start over.
What’s your thought.

Pete

 

[Aiken Drum]

What are your water parameters precisely?

Your microbes responsible for your cycle grow and die off depending on how much bioload there is in the aquarium. When you add new fish your bioload increases, and it takes some time for these microbes to grow in number sufficient to consume the higher level of waste. When you remove fish or fish die, your bioload reduces. These microbes then die off over time as there is insufficient food to support them all.

Once your aquarium is empty of fish, those microbes will just all die and you will lose your cycle in few weeks. You can't cycle an aquarium with no fish in it, or another ammonia source. If you just let your aquarium run with no fish in it, you will need to cycle it again.

It's likely that you introduced some pathogen into the aquarium when you added the new fish. If this pathogen ends up killing off everything I would consider emptying the aquarium, sterilising everything, and starting over, rather than trying to retain your cycle and and adding fish into an environment that may still be infected.

 

[Andy Sager]

Thanks for responding to my message. I don’t think the pleco and goldfish were an issue as the have been together for 3 years without any issues. Since writing this post yesterday I have lost the remaining goldfish and two danios. I think you are correct that I did not quarantine the danios long enough. I suspect the remaining danios will follow soon. The fuzz seams to have cleared up. I have retested the water again and it can’t get much better. My plan at this point is to let the tank cycle for a couple of months and start over.
What’s your thought.

Pete

Here's what many don't seem to realize when mixing fish that are questionable to mix: At some point, things can change and what used to be happy tankmates turns into a nightmare. That's the chance you take. There are many instances where large cichlids were kept with Guppies or smaller Tetras for months or longer then one day, the cichlid just ate them all. Why? What changed? The answer: Usually it 's because the hobbyist missed a feeding or two. I'll go one further, I had a breeding pair of Oscar fish who adopted a small school of baby feeder goldfish I had put into their tank to feed on instead of eating them. Why? I had removed their spawn of fry the day before and the goldfish were still in their juvenile bronze color phase so I surmise they thought the school of goldfish was their lost babies. LOL ( It really was the cutest thing LOL )
With that, no, it looks like the pleco was not the issue. It sounds like your Danios brought something in with them. Keep my post on quarantine tanks vs hospital tanks bookmarked so you can refer to it after you reset up the main tank.
As for what to do with the tank if all the fish die, I'm with Aiken: Sterilize everything. Get yourself a gallon of Bleach or chlorine with no additives or scents and pour it in while the filter is running but any filter cartridges or sponges are removed. ( You can stop adding the chlorine when any algae or biofilm on the glass starts to turn white. ) That will sterilize everything. Then rinse out the tank multiple times then use 3 to 5 times the amount of dechlorinator when you fill the tank for the new fish. You should have a sterile environment to start with. ( I usually do a test fish just to confirm that the water is safe but doing a chlorine test can also tell you. )