So, I did a water change and tank clean today and about 4 hours later, the fish started gasping and going to the top of the tank.

We checked everything
Nitrates- 5
Nitrite- 0.2
PH- 6.2
Ammonia- 0


We have 2 5inch Oscars, a 5 inch Bala shark, a cory catfish, 3 2 inch blood parrots and 3 4-6 inch Pleco's in a 90 gallon tank. We have a fluval 304 filter. 2 carbon bubblers and a bubble maker.

Please help, our fish have become apart of our family and we desperately need help!

can you brief us how did you carry out the cleaning?
did you clean all the filtering system or just the tank?
have you treated the new water against chlorine before filling up the tank?
if you did clean the filter system, did you use tap water or tank water?

we did about a 30% water change vacuumed the bottom of tank. Noticed that the fish were gasping about 5 hours later, did water tests and thought maybe the issue was the filter cleaned the filter with tap water but put water conditioner in it before putting it back into system

we used tap water with water conditioner for tank cleaning as well

Did you add water the same temp I know it sounds silly but lost my ghost knife due to temp drop he was gasping found the temp had dropped heaps heater failure

Gazza

ok its going to be 1 of a few things. chloramine in the tap water. use more conditioner or make sure you used the right amounts. I would recommend "prime" its far better than any other conditioner on the market and works out cheapest too.

2nd your tank isn't fully cycled as you have nitrites present. keep a watch over the next few days cos I reckon you may see ammonia too.

3rd you say you washed the filter in tap water and then added conditioner. tap water will kill the bacteria in your filter. if you are going to use tap water to clean your filter you must add it to the water before you put any part of your filter near it. this is why we recommend using old tank water to clean filter parts and media.

if you have washed your filter out using tap water and then added the conditioner your filter cycle will be damaged and you will need to recycle the tank.

www.oscarfishlover.com/helpful-articles/cycling-an-aquarium

all seems well today actually, all of the fish are breathing normally and none of them are hanging out at the top. we all think that it could have been because the filter was clogged. after we got the filter running smoothly last night, everything seemed to have settled down, everyone is back to normal thankfully. All in all though, it was a long night. No one went to bed untill we knew for sure if all of the fish were going to make it, so no one went to bed until like 2 in the morning, just watching th fish. I don't know what we would of done if something would have happened to any of them.

By the way, we checked all of the levels today
Nitrates- 3
Nitrite- 0.1
PH- 6.2
Ammonia- 0

I am so thankful for everyones help and concern!

hey, i don't see any temperature readings.
Adding water with a difference in temperature of more than 2 degrees, can make your fish act weird, like gasping and hanging at the surface.
Did you refill with the same temp water as the original tankwater?

A clogged filter can indeed hurt your bacteria, but would usually result in an ammonia spike.

I had my share of sleepless nights, when things were troublesome or risky for my fish.
You're a good fishkeeper, if i see how you can worry about your fishes well being!
Respect for that!

Im hoping your clogged filter is still running ok. can you retest and post the results. hopefully your filter has caught up and it is cycled again

Nitrates- 3
Nitrite- 0
PH- 6.2
Ammonia- 0
There you go, everything is back to normal =)

still curious about the watertemps before and after waterchanges...
Let hope this ordeal was a single occurring event and will not happen again!

We had someone else a while back that had problems every time they done a water change. I cant remember 100% but I think they changed water conditioner to "Prime" and it solved the problem???? my brains gone dead. anyone else remember it?