After 4 Months, All 4 Of My Tiger Barbs Were Found Dead This Morning;

[G-NUT]

I woke up this morning to find all 4 of my tiger barbs dead.  Anyone have any thoughts of why?
 

• 55 gallon tank
• cycled for 3 weeks before adding fish
• have had fish in the tank for just over 4 months now
• 2 of the tiger barbs that died were of the first several fish I had populated the tank with
• the other 2 of my tiger barbs that died were purchased about a month and a half ago
• the other fish are all Lake Tanganyika cichlid of various species
• I had a total of 12 fish in the tank before the barbs died
• all 4 barbs were the largest fish in the tank
• ph, ammonia, and nitrites leves checked out fine
• plenty of water flow with a good size bubbler and a high-flow h.o.b. filter
• filters changed about every 2 weeks
• changed about 4 gallons of water per week
• use stress coat and conditioner at water changes
• ensure the water change temp is accurate
• tank temp maintains about 80 deg
• the barbs actually rule the tank
• diet hasn't changed

My family and I regularly watch the fish.  I also watch them almost daily while I'm eating lunch and listening to ESPNU Collage Football Daily; ( I'm fortunate to work from home. )  My fish have all been fine.  The tank has been good.  Nothing out of the ordinary since starting the tank.  Woke up this morning and all my fish are fine except for all 4 of my tiger barbs, which were dead and floating at the top of the tank.  None of them had nipped fins, none ate on, no bloated stomachs; they all looked fine, except dead.  I took a water sample to PetSmart and they said everything looked good.  I then went down the road with my other sample of water to Southern Agriculture and they said the same thing.
 
Anyone with any thoughts?
 
Thank you.

 

[eaglesaquarium]

• filters changed about every 2 weeks
• changed about 4 gallons of water per week

 
Not sure about what killed the fish, but here's two things that jumped out at me.
 
1 - Filters do not need to be changed every 2 weeks.  A properly cycled filter normally requires about 6 weeks, and removing this all the time means that your tank will constantly be playing catch up on the nitrogen cycle.  A better option is to merely 'rinse' in old tank water on a regular basis, every 2 weeks is fine.  (You said you 'cycled' the tank for 3 weeks before adding fish... what method did you use?)
 
 
2 - Changing only 4 gallons out of 55 is not nearly enough of a water change weekly.  If your water parameters are correct (will get to that momentarily) they will not remain that way for long.  You should be changing at LEAST 20% of the water volume weekly.  If you have a more heavily stocked tank, then you need to be more aggressive with the water changes and change either a larger volume and/or higher frequency.
 
 
As for your water coming back as 'ok' as confirmed by Petsmart and Southern Agriculture... did they tell you the exact readings?  If not, then I would put no trust in their answer?  Did they use liquid test kits, or did they use strips?  If they used test strips, again, you can't trust that reading.
 
These are just my initial thoughts...

 

[Fishmanic]

Some types of filters allow you to change just part of the filter media at a time which would be better for keeping your tank cycled.   If you change the entire filter media ( some filters just have one pad filter) you risk having a minicyce which could kill some delicate fish.   If you are using a filter with a single pad for media, think of upgrading to one that has three or more media types in the same filter.  Two weeks is too frequent for filter media change especially if you're changing all the media at once.

 

[eaglesaquarium]

There's no need to change filter media, with the exception of carbon or zeolite.  All other media can (and in my opinion) merely be rinsed to remove particles that can clog it, but doesn't need to be replaced until it is literally disintegrating.

 

[pingu2013]

anything got in the water my partner wiped out my tank with air freshener before. Spraying it to close to the air pump. Now shes banned from using it any where near my tanks

 

[Ch4rlie]

anything got in the water my partner wiped out my tank with air freshener before. Spraying it to close to the air pump. Now shes banned from using it any where near my tanks

 
That is unfortunately something that does happen, aisprays, deodorants glass cleaners etc, will more than likely have an effect on most if not all the tank stocking.
 
This would not explain though, why would just affect the tiger barbs and none of the other stocking op has.
 
I do agree with Eaglesaquarium that it could be to do with the filter media being changed every 2 weeks which could result in mini cycles or a build up of ammonia, nitrite and nitrates and therefore affecting the stocking.
 
Also the fact only 4 gals of water is being changed weekly, this is nowhere near enough really as believe this will cause a build of nitrates and this could be the cause of these losses, but again, does not fully explain why just the barbs were affected.
 
My 2 cents worth of idea -could be simply be down to the 4 Tiger Barbs being the original occupants and perhaps going through a possible uncompleted cycle (since op only did 3 weeks cycle) so unsure if did do a full cycle as believe op may not have a test kit (he takes a water test to Petsmart) so how would he know for absolute certain that the tank was culled before  stocking the barbs if no water tests carried out.
If this is the case the barbs may have been damaged by ammonia or nitrite poisoning during the final stages of cycle and now have died due to this possible cause?
 
Just an idea though.
 
Would be good if you can confirm if you did indeed complete a fishless cycle and if you have a liquid test kit and that you regularly test water parameters.

 

[l_l_l]

I'm pretty sure you have really high levels of Nitrates and by just changing 4 gallons per week you were only slowing the nitrate poisonning your fish were having.
I really suggest you test your own water with liquid test kits, as you really want numbers and not "it's fine".
Those LFS are the same one telling you that a Betta fish can live in a 1 gallon tank.