Barb mass exodus

[LeafsFan]

My tank has been running for a year and a half now and I recently moved it to my new house. The old house has poor tap water so it was always a fight to maintain good tank water quality.

New house has excellent water quality and my tank has been flourishing dive the move, which was 3 months ago.

Until today. Just came down to feed then and every single barb was dead. The Gourami and 3 clown loaches are fine. Just tested the water and it has a 0.25 ammonia reading which I would attribute to the dead fish in there.

Another weird point is the barbs looked a though they had entrails coming from their butts.

Tank size is 38g
Ammonia 0.25
PH 7.4
Nitrite 0
Nitrate 20ppm

Temp 80
Fed every second day.

Original stock list
8 tiger barbs
3 odessa barbs
1 rosy barb
1 moonlight gourami
3 clown loaches

The only thing I have done different was put in the LPS water bio support, bio clean and conditioner. Something I hadn't done in a couple weeks.

Finally, the other fish seem fine. The loaches are chafing each other around and such.

Ps. I know the tank is small for 3 loaches. They were added maybe 5 months ago. New basement is being redone with a huge tank as the focus point. My lps rarely has loaches in stock so I grabbed then then for the future tank. Which will be running in the next month or two.

Basically, what went wrong cause I am lost

 

[LeafsFan]

No guesses yet

Another piece of info I just thought about is that they are putting in new sewer lines behind my house for new housing. Could this have released minerals into the main water supply that would not be detected by an api kit? The last 4 fish are perfectly fine still

 

[ejaramillo01]

Did you noticed any bad sign in the barbs before they died? Like loss of appetite, change in colors, or shape? Nothing?

 

[LeafsFan]

Nothing was different. Last time I fed them they were going nuts as usual waiting for me to put food in.

All I can really believe it was is an over dose of the lps conditioners. I hadn't used then in awhile and used the cap to the required amounts. Maybe I messed up there.

Tested parameters again today and everything is still good. The remaining 4 fish are good. They were timid after the other fish had died but back to normal.

Only other thing I can think of was possibly I didn't match the temp right when toping off the water and it caused a shock.