[maverickbr77]

Alright TPT I am very confused, over the last week I have been having a few deaths in my 55 planted display tank. Started with a very old rainbow shark, I checked my water parameters and was at 0 NH4, 0 NO2, and 30 NO3 so I did a water change but figured it was due to old age. A couple days later I lost an angel rechecked water and was at 0 NH4, 0 NO2, and 20 NO3. 3 days later I have 2 dead rams water reads 0 NH4, 0 NO2, and 20 NO3.

No chemicals have been used near the tank.
No new additions for the last couple of months.
Fish look nice and healthy with no outward signs off illness, no odd behavior, clamped fins, blotches, spots, etc., with the exception of the angel not eating well the evening before it died.
The other 7 tanks in the house have had no losses.

I am at a loss as to what to do here and hoping someone has an idea what is going on.

 

[roadmaster]

Might wonder if water treatment plant has increased chlorine or chloramines which might mean more dechlorinator is needed than usual.
Might check to see that fish food has not expired or been tampered with.
Might check thermometer to see that temp is within normal range.
Is all I got.

 

[maverickbr77]

Water is remineralized RO and is from a well
Food is good
temp is 77f

 

[roadmaster]

Is the tank planted? any new plant's recently?(some places spray plant's to prevent insect damage).
R/O membranes fairly new?
Is odd indeed that only one tank out of seven is affected.

 

[maverickbr77]

heavily planted last addition was some moss from a forum member here and is in another of my tanks as well.
R/O is newly setup early this year.

 

[Bushkill]

Were the fish eating / acting normal right up to the time they kicked or were these deaths over a the course of days?

 

[maverickbr77]

all were acting normal up until I found them dead with the exception of the angel not eating well the night before it died. All remaining fish are still acting perfectly normal.

 

[Bushkill]

So even the angel was a relatively "swift death". If it were me, I'd be thinking along the lines of a contamination / poisoning of some sort in your water change. Bacteria and fungus of the ilk we usually deal with don't work that fast.