Urgent Help Needed! I'm In Deep Strife! Ammonia + Nitrite

[ey2006]

While I was cleaning the tank yesterday, I turned the canister filter "inlet" pipe off temporarily to take out the java moss and food stuck to the pipe, but forgot to turn it back on.

When I checked on the fish today, first thing I noticed was a very very foul smell, which smelled like dead fish, quickly did a count and no fish was missing.

I then did a water test and the results were:

Ammonia 1.0
Nitrite 0.25
Nitrate 40

I have just done a 50% water change and tested the water and fortunately, the results have improved somewhat. Ammonia is now 0.5 and Nitrite 0.12.

At this stage, what can or should I do to help the poor fish? I still can't believe I left the filter switch off but I gotta find a solution to this before it becomes hazardous.

The tank is a 300L community with loaches, cories and tetras.

 

[ey2006]

Having just performed a 50% water change, how long do I have to wait before doing yet another 30%-40% water change?

I know changing too much water at a time or in a short period of time is stressful on the fish, however, I am taking out toxic water and replacing it with tap water (which doesnt have ammonia or nitrite present)....so will I potentially kill the fish if I do a water change every few hours?

 

[Qays]

Do a water change tomorrow. Your tank is probably just going through a mini cycle.

 

[ey2006]

Thanks Qays.

How much water should I change tomorrow?

Ammonia is now 0.5 and Nitrite is 0.12....since the filter was left off for at least 12 hours, could this have killed all the beneficial bacteria in the tank?

Any other suggestions would be greatly appreciated.