Green Tiger Barb issues

[scpleco]

Hello,
Last week, I set up a new 50 gallon freshwater tank. Saturday, I added 4 green tiger barbs and 1 rainbow shark. Since bringing them home, 1 of the barbs have seem to mainly swim by themselves. It is quite smaller than the rest and seems to have bulgy eyes. Gradually it has showed increased weakness in swimming and gets bullied by the rest. Today, I removed it to a separate tank, but now is having bouyancy issues. There is one other bard that maybe seems a little weaker, but overall seems fine.
YouTube takes away some of the quality but here is a link to it swimming prior to removal.

Tank: 50 gallons. Freshwater with a live rock and spider wood. All new substrate (medium rocks and sand) with artificial plants. I have a MarineLand canister filter. Temperature is kept at 75. PH=7.4 Ammonium and Nitrites=0 Nitrates=0-5ppm - I use the API master test kit.
Any help is appreciated. Thank you!

 

[Colin_T]

The bulging eyes would suggest an infection in the brain. Possibly a bacterial, protozoan or viral infection. Protozoan infections are normally caused by poor water quality. This shouldn't happen in a tank that is 1 week old.

Bacterial or viral is possible but the fish would have probably had the infection when you got it because they both occur in crowded dirty tanks and again should not happen in a new tank that is clean..

You can try a broad spectrum medication or salt, and do a big water change to see if it helps.
Use 1 heaped tablespoon of rock salt (aquarium salt) for every 20 litres (5 gallons) of tank water. Keep salt in tank for 2 weeks.

 

[Slaphppy7]

How did you cycle a tank so quickly?

What do you mean by "live rock"?

 

[scpleco]

Thank you! Unfortunately the barb just passed away, should I still treat the tank to be safe? I did add aquarium salt before the fish were added, is it okay to add more? The spider wood had also developed some white fungus, but according to instructions it is normal and harmless.
I used API quick start and the live rock was one that was already in a tank, I did clean it though.

 

[Colin_T]

No need to add medications. Just do a 75% water change on the tank every day for a week. This will dilute any disease organisms that might be in the tank.
Make sure any new water is free of chlorine/ chloramine before it's added to the tank.

Monitor the remaining fish and post pictures and video if any more develop the same symptoms.

 

[scpleco]

Okay I will give that a try, they all look pretty good today. Thank you!!