Entire species of fish dead overnight. (Minnows)

[Angelphish]

Last night all of the fish were doing O.K. No one was acting out of the ordinary, so I went ahead and did a quick water change before I went to bed. I wake up this morning to find all of the fish doing fine, except for the feeder minnows/rosy reds. Every other fish was swimming around like nothing happened, as I'm staring at all the minnows, dead, but one. The last living minnow was about to give up on life under the Ghost Knife house (clear plastic tube). Did a fish go on a killing spree, or was it a disease that only affected them?

pH- 6.2
Ammonia - 0
Nitrite - 0
Nitrate - Under 5

Stock list - Five Angels 1 1/2 - 2", Three 2 1/2" Tiger barbs, Five 3/4 - 1 1/2" Tiger barbs, One 3 1/2" Elephant Nose, Four 3/4 - 1" Emerald Cories, A few assorted snails, One 3 1/2" Half Banded Spiny eel, One 4" African Featherfin catfish/Squeaker, One 6" Common Pleco, and One 5" Blood Parrot.

 

[tlindsey]

What in your aquarium needs to eat feeder fish, imo you are jeopardizing the health of your other inhabitants by introducing rosy reds , and minnows. Possibly they were already sick or died from shock from the wc.

 

[Chub_by]

Was the WC water warmer than the tank? Rosy reds are obviously not tropical so that could have shocked them while not harming the others.

 

[smitty03281964]

If it is rosy reds then I would believe that the water change caused the problem.

 

[Angelphish]

The WC water is colder, although I do heat it for twelve hours with a tetra 50W heater before I change it. I only do about 9 - 10 percent water changes, but I do them every twelve hours. The water temperature slowly drops about 1.5 degrees F during the ten minute process of filling the tank. The temperature change is gradual, since I have a pump. I had those minnows for about 3 - 4 months before this happened. I continued with two water changes a day since the minnows went in. If that was the problem, they would have died earlier. These minnows were temporary anyways, I was planning on getting a BGK, which would likely eat them. I am not upset, though I am rather suspicious of the Blood Parrot, being the largest and most aggressive fish in the tank ATM.

 

[HumanBean]

WC shock

 

[Angelphish]

If it's WC shock, then wouldn't they have died within the first month?
I do about 60 water changes a month, and I had the minnows for four months. That adds up to just under 250 water changes. I just can't see it being water changes.

 

[HumanBean]

What's your water source ?

 

[Angelphish]

We tapped into the water line inside the house. I have a valve to control the flow inside the bin that I heat it in.

 

[krichardson]

If the parrot is the culprit the minnows should have bite marks or wounds on their bodies.