Scared

[benzenering]

I am a reasonably experienced fishkeeper (15 years) but I am stumped by something that has recently happened to one of my tanks.  Maybe someone can see something I am not seeing.
 
Three months ago, I stocked my 38 gallon tall, which has two large pieces of mopani wood and a few plastic plants in it for hiding spaces and decoration (there is plenty of swimming space), with 30 small fish...10 tiger barbs, 10 green tiger barbs, and 10 cherry barbs.  For a month or so they were OK.  Then, one by one, they disappeared.  There was no sign of illness in the tank and no sign of aggression.  They just disappeared.  I am now left with one tiger barb and one cherry barb.
 
Water parameters are as follows after a 50% water change and treatment with SeaChem Prime to dechlorinate:
 
pH 7.4
NH4 0.50
NO2 0
NO3 20
GH 107
KH 90
 
I have NH4 in my fresh tapwater at 2.0; I pulled the 2014 water quality report for my town and they report chlorine at 0.44 ppm and chloramine at 3.03 ppm so that somewhat jives with what I'm seeing on my tests.
 
I got all the fish at a large online retailer...could I just have gotten a bad batch?  I just can't figure this out.  I want to restock, but...well...I'm SCARED!

 

[attibones]

How many do you have left of each species? Tiger barbs can be pretty mean to other species, particularly when they are in a smaller tank, although larger numbers are supposed to even out some of the aggression. 

 

[benzenering]

I have one tiger and one cherry left

 

[Ch4rlie]

There should be no ammonia coming from tap water.
 
This is the most likely source as to why your stocking numbers is falling. However, a few questions first to get more of a picture of what is happening.
 
Did your stocking show any symptoms at all before they passed?
i.e red gills, gasping, at surface of water etc
 
Did you add all the stocking in one go or over a period of time?
 
Do you have any other tanks?
If so, are the stocking in these tank/s healthy or do they show any similar symptoms or passed?
 
This may sound silly for someone with 15 years experience, but got to ask, did you cyle this tank?
How did you cycle the tank?

 

[benzenering]

There should be no ammonia coming from tap water.  Like I mentioned, I have lots of chloramine in my tap water, as is indicated in my town's water quality report as well.  I understand this to give a positive reading on the ammonia test.
 
This is the most likely source as to why your stocking numbers is falling. However, a few questions first to get more of a picture of what is happening.
 
Did your stocking show any symptoms at all before they passed?  No symptoms
i.e red gills, gasping, at surface of water etc
 
Did you add all the stocking in one go or over a period of time?  All at once
 
Do you have any other tanks?  I have two other tanks, a 55 gallon and a 10 gallon
If so, are the stocking in these tank/s healthy or do they show any similar symptoms or passed?  All are OK, and have been for many years
 
This may sound silly for someone with 15 years experience, but got to ask, did you cyle this tank?  Tank has been cycled for 15 years, this was my very first tank.
How did you cycle the tank?  Previous inhabitants were given away  the moment the new ones were added, and previous inhabitants are fine in their new home

 

[Byron]

I agree with others about possible toxic effects from ammonia.  However, this should not be a problem here from what you describe.  Ammonia present in the tap water will be detoxified by a conditioner like Prime, and this is permanent.  Same for the chloramines/chlorine.  And I would expect real signs of ammonia toxicity, like increased respiration, flashing, gasping, red gills...depending upon the level.
 
I have gone through something similar several years ago, and in my case, after testing for every conceivable possibility, it turned out to be some toxin (not identified) leeching from a chunk of wood.  And if you've had the wood for years, remember that toxins deep inside can be slow to leech out.  Just one possibility.
 
Another is an internal protozoan.  I have had two bouts of this.  Fish began dying, about one a day, with absolutely no external signs of anything.  Every morning I fished out one or two corpses.  There are many internal protozoan, but food medicated with an antibiotic is usually a good remedy.  Some fish may not tolerate certain antibiotics, but these you mention should.  Late now of course, they are nearly all dead.  But metronidazole added to food is often very effective.  I used this both times.
 
On the protozoan, I am finding that the "bread and butter" fish being commercially raised are far more likely to carry these than wild fish, or fish from individual breeders.  I will no longer even look at fish in stores that use mass suppliers, I have lost so many and had so many issues.  And of course Tiger Barb and Cherry Barb are true "bread-and-butter" fish, commercially raised for years.
 
There could well be other possibilities, but these are two I have experienced.
 
Byron.

 

[Munroco]

When you say "disappeared", do you mean there are no signs of dead fish? If fish are dying in your tank, there will be dead fish floating around.
 
Its a silly idea but is there  any chance that fish are jumping out of your tank?

 

[Jenste]

Also, just for future re-stocking, barbs can get fairly territorial and active, I would stick with one of the schools of 10-12 in  a tall tank rather than mixing 3 schools together. 

 

[benzenering]

When you say "disappeared", do you mean there are no signs of dead fish? If fish are dying in your tank, there will be dead fish floating around.
 
Its a silly idea but is there  any chance that fish are jumping out of your tank?

Meaning, the current inhabitants are eating the former inhabitants.
 
Byron, you may be onto something by mentioning the wood.  I acquired the wood at the same time as the fish, as a matter of fact it is still leaching tannins.  I'll up the water changes from 50% weekly to 50% daily.
 
It could be aggression, but I'm experienced with aggression as my 55 gallon has African cichlids in it so I know how to make territories in it to keep it down a bit.  Maybe it is dissimilar?

 

[benzenering]

bump

 

[RobRocksFishTank]

Okay, I'll say it.
 
It sounds like the tank was not cycled. The fact that you did not find any dead fish probably exacerbated the problem. The bodies were probably rotting away somewhere. Those types of fish aren't really known for eating dead fish. Not unheard of but unlikely. That is unless they aren't getting enough other food.
 
Of course, if there are any toxins present, they could cause the same type of thing but again, the no bodies things has me concerned.
 
Aggression with barbs is a possibility, but it's usually prolonged and very obvious. If this a sever case, that might explain the missing bodies.

 

[benzenering]

No one is paying attention...my tank is very much cycled...ammonia reading out of the tap is already 2.0 ppm.  Any idea why?  Hard to get to a tank reading of 0 ppm when tap water is 2.0 ppm! 
 
I have two other tanks.  Ammonia is always 0.50 ppm after water changes and no problems with either of those tanks, just this one.

 

[RobRocksFishTank]

Your statement about the tank being cycled was mixed in with someone else's quote. I did not see that information as I didn't reread the quote. I had just read the original. Scratch what I said about lack of cycling. It's obviously not an ammonia problem.

 

[Byron]

No one is paying attention...my tank is very much cycled...ammonia reading out of the tap is already 2.0 ppm.  Any idea why?  Hard to get to a tank reading of 0 ppm when tap water is 2.0 ppm! 
 
I have two other tanks.  Ammonia is always 0.50 ppm after water changes and no problems with either of those tanks, just this one.

 
Ammonia in the tap (source) water must be dealt with at every water change.  The easiest way is to use a conditioner that specifically detoxifies ammonia.  You are using Prime, which does this, so that is good.  But perhaps you are not recognizing what follows, so if I may I will explain.
 
Prime, like many (but not all) products that detoxify ammonia, do so by changing the ammonia (which is highly toxic) to ammonium (which is basically harmless).  This is a permanent change, i.e., the ammonium will not itself turn back into ammonia.  Both plants and nitrifying bacteria will take up this ammonia/ammonium, and there should be no issues resulting.  Using the Prime or similar conditioner at each water change immediately deals with the influx of ammonia, which is important.
 
Now, test kits for ammonia generally read ammonia/ammonium as "ammonia," so the presence of "ammonia" via a test like the API is nothing to worry about provided you are using Prime or similar.
 
In acidic water, this change from ammonia to ammonium is automatic.  It has to do with the positive and negative ions, but it isn't really necessary to understand all that chemistry, provided we comprehend what is occurring.
 
Back to the problem of fish disappearing...I see this all the time, though no where on this scale (except for the couple of specific problems I mentioned previously).  Sometimes I may see the corpse floating, but more often I never find it.  Mind you, I don't go looking for it, as a single fish is not going to cause any real trouble (provided everything else is in balance), but sometimes I will find a tiny piece of vertebrae weeks later when I poke behind some wood for some reason, and remember it was likely that fish that disappeared.  Most fish will eat dead fish, as will snails, and of course bacteria break them down and fairly rapidly.  We've no idea of the time frame between your fish disappearing...you do mention 28 fish missing over three months, so a fish every 3-4 days might be gone before you see it.  If the fish are not jumping out, there really is no other logical explanation.
 
As for the cause, I am still leaning toward an internal protozoan.  And even if the remaining two fish do not die, this protozoan might still be present, depending upon what it is exactly, and could affect new fish.  I don't know enough about protozoan to offer advice, but it is something I would consider.
 
Byron.

 

[benzenering]

Thanks, Byron.  
 
I want to restock, just not sure how to go about it.  Sounds like I should just just medicate the tank before getting more fish?  
 
I have some metronidazole powder now to treat the tank.  Instructions on the jar say to treat the tank for 5-10 days...what do y'all think?