had a loss of 19 tetra's and an angel fish


Small Fish
Dec 21, 2010
changed water yesterday and washed sponge filter out with cold water from the tap which i hear is the cause of this......

i put in 10 new angel fish i bought yesterday from a lady who was selling them.

they looked nice and comfy in my tank (this was 4pm)

i didn't go to bed until 3am as i was watching a film with the gf - all the fish were happy and swimming and i didn't think where was any problems.....

i woke up at 10am - i saw 4 floating tetra's thinking oh no the angels have eaten them.......couldn't see any more ! i had 19 in there at 3am !!

i blamed it on the angel fish and was just writting a message to the lady i got it off before i took out my remaining for dead floating fish when i was looking at the tank and an angel fish just sunk to the bottom n landed on its side n flapped for a second or two before dying infront o my eyes - i scooped it out and put it in fresh warm water but no life....

i then come to the conclusion it wasn't the angel fish because when i went to scoop the angel out, i disturbed the water and the other fish i couldnt see came out behind ornaments and started floating.....

i scooped them all out = 19 tetra's plus the angel fish!

i did a 75% water change thinking it was the water that killed them


i just done some water tests

Ammonia = 0
PH = 7.2 (so i put some PH 7 in cos it detoxifies heavy metals and removes chlorine from the water change)
nitrite = 0

don't have a test for nitrate

it is now 4:30pm and this was 10:30pm when i did water change an they all seem fine just like 24 hours ago

do you think it was cos i washed the good bacteria out the filter or something else? theres no white spots or damage on any of the dead fish



Last edited:


Large Fish
Nov 13, 2010
Northeastern Tennessee.
Hello; There in not enough information in your post to point directly to a cause. Here is a general response to your problem. I have washed the sponge of a sponge filter with tap water and had no problems. I always made sure to ring it out thoroughly. Folks on this forum have suggested rinsing these things with tank water (I guess at water changes).
Review the methods you are using around the tank. An aquarium is a tiny amount of water compared to any natural environment your fish came from. In the wild thousands of gallons of water can exist for each fish and the movement of water along with some natural cycles moves nutrients in and waste out. We try to match this in an aquarium. An aquarium is a modification of the natural open system. We are responsible for adding energy into the system in the form of filters and lights. We also have to add food (nutrients) for the plants and fish and some way to remove (filtering) or deal with waste in what appears to be called cycling these days.
First question to be answered is if the water you use is suitable for keeping fish. Some water supplies have problems at the source. There are ways to deal with this, but many are costly or require some extra effort on your part. I am sure some others on this forum can guide you thru a process that they favor. I process water without chemicals and have for decades. I have and use the test strips and liquid water test kits if a problem shows up. If your main source water turns out to be bad, that can be discussed if you wish to continue.
Second question has to do with how you handle materials around the tank. Contamination can come from having some residue on your hands when you stick them in the tank. Was the bucket that you carried the change water in ever used for something else? If you used the chemicals to treat tap water, did you mix the chemical in the replacement water before adding it to the tank? I have buckets, cloths, sponges and other equipment that are only used for my tanks. Chemicals sprayed into the air can be pushed thru the tank by an air pump. Ornaments placed in a tank can release toxic stuff. Lights and heaters can short out and introduce electricity into the tank. Play detective and see if a procedure used may be suspect.

Mel in Tx

Small Fish
Jan 5, 2011
Burleson Tx
I know I had a problem with one of my buckets. It said FISH in big letters on the bucket, and my husband used it to wash the car without telling me... well I stuck my fish in and two of my Parrot Cichlids died. It was horrible. I threatened to divorce him if it ever happened again... so I don't think he will be touching my fish stuff anymore. ;)


Superstar Fish
Oct 15, 2009
Northern Arizona
Do you adjust the pH on your tank using chemicals? What was the pH of the tank the angels came from? What size tank is this in?

It sounds like they could have died from a pH swing, if you use chemicals to adjust your pH. Your pH should be the least of your worries as long as you keep it steady. Any fish can adjust to any pH, so having a "correct" pH is way less important than having a steady pH. Abrupt swings in pH are often responsible for "mysterious" fish deaths.

Also, I hope you have a REALLY big tank to house 10 angels (well, nine now). They are big fish and get to be 6" from nose to tail and 10" from top to bottom. They are cichlids and as such can be territorial, especially if they form a breeding pair.

Aug 13, 2010
Sicklerville, NJ
SO....Bass and SK covered most of the issues, but the only time I have seen massive death like this is when my friend did not add dechlor to his water and his whole tank died in about 8 hours. :(

Also as Bass stated...the actual PH is not as important as a stable PH. Keep that in mind.

Sorry for your loss.