Help needed ! Only SOME of my fish die!

Guys
So here is where I am : 2 year established 55 gallon with a marineland 75 and a power head attached to an eheim filter. I have 5 2-3 inch gouramis and a 4 inch Hoplo that are all doing well. Lively, no issues.
the problem is that every time I introduce any new fish into the tank, they die within 2 days max. they show increased attempts at breathing and erratic swimming and then....gone, dead, no more.
Ammonia, nitrates and hardness all test fine with a master kit. Water is beautifully clear.
Regular water changes.
Whats going on?? So far I have tried danios, algae eaters, even a bloody goldfish.

 

were any of the gouramis or the hopolo ever sick while with and treated ?

 

What kind of substrate?
What do they look like at the store you get them?
What does their poop look like?

 

Nope
No sickness in tank at all - just can't keep the buggers alive

 

I think they are prone to internal worms, there may be worms living in your substrate that they are feeding on that is causing internal problems

 

My guess is the Hoplo catfish might be chasing & stressing out the newcomers once the lights are out.

 

Sand substrate - nil gas pockets - regularly raked and vac'd
The same 5 gouramis and the hoplo have been in their for going on two years

They show stress almost as soon as they are in the tank. Yes, they are acclimatized first.

 

What kind of gouramis? How many hoplos?

 

Its not gas pockets that is the problem with sand, its just full of nasty fould smelling bacteria. I would always reccomend people use gravel with a undergravel filter with sensitive fish.
If your new fish are dying, they may just not be as use to the bad bacteria as the old ones are, and they are probably stressed from shipping and pet store.

 

Maybe a big PH sifference between the fish store water & your tank.

 

Thanks guys. are gouramis and hoplos known to be sensitive?

 

Not Hoplos.

 

Yes along with high nitrates and rotting sand.

Maybe a big PH sifference between the fish store water & your tank.

 

Its not gas pockets that is the problem with sand, its just full of nasty fould smelling bacteria. I would always reccomend people use gravel with a undergravel filter with sensitive fish.
If your new fish are dying, they may just not be as use to the bad bacteria as the old ones are, and they are probably stressed from shipping and pet store.

UGFs are the worst. You have to tear up your entire tank to clean them.

DavidHumphrey can you please answer this:

What kind of gouramis? How many hoplos?

 

Old tank syndrome, maybe?

 

You said 'regular water changes'. How much and how often? What's the pH of your tank and tap water?

 

Geez chaps...………………………………..

So once a week and about 50% right now.

 

UGFs are the worst. You have to tear up your entire tank to clean them.

DavidHumphrey can you please answer this:

Again as politely as possible [getting very difficult with you ] I completely dis agree with your info .
Link me where you got that one from ...You are saying a keeper with UG can't just vacuum and change water like everyone else ?
Maybe you should only post answers and advice on things you know ..
Clearly you have no hesitation posting completely incorrect info ..
Have you ever thought what you say might be a factor in other peoples fish dying ?
People come here looking for help not off the cuff blabbing from a clearly unexperienced person disguised as advice from an experienced keeper ..
The tank has been up and running for 2 years according to original post ..I wonder how many times the op had to completely tear up the whole tank ?

Whitewolf offers good info to be considered .

 

Do you QT first? Just wondering if they’d die in QT too... in that case could just be bad fish and not a bad tank lol

Let’s keep it civil guys and help the OP! Always helps to give sources to back up knowledge.

 

Nope
No sickness in tank at all - just can't keep the buggers alive

Do you use API stress coat+ at all? because this is good for adding to water before you add fish in.

Improves water quality: Tap water usually contains chlorine, chloramines and heavy metals harmful to fish, and its chemistry will likely vary day to day. Regular use of Stress Coat multipurpose conditioner instantly removes these elements. Add 2 tsp per 10 gallons directly to aquarium after water changes.

Fights fish stress: Every time a fish is netted or handled, its protective slime coating is disturbed, causing a loss of essential electrolytes through the skin. This leads to suppression of the immune system, resulting in increased susceptibility to disease. Stress Coat contains Aloe Vera to help repair the natural slime coating that fish need when stressed from handling, shipping, fighting, or other forms of stress.

 

I'm not going to argue. As one of the mods say 'agree to disagree and move on'. Good day.

 

Since your water parameters are fine & have a current group of fish that are apparently thriving, the answer is likely:
- Aggression
- Bought sick fish
- Too much of a water chemistry difference between the vendor's tank & OP's.

 

Have any other fish ever lived in the tank over the last 2 years ?
I was getting to a term we call subclinical carriers .
That is when a fish is cured of an issue but still has the pathogen that can and will infect other fish .
I am not clear on the Hopolo to be honest but most gouramis are from Asia and the pathogens there are not the same pathogens here.
Often when fish not raised with a certain pathogen but is then exposed to it the fail fast .