[OKCIS]

About 3 weeks ago i switched from a penguin 150 filter to a marineland C160 canister. I installed it and the amount of flow was amazing. However it was shooting out under the water. Tested my water levels everything was back to normal in about 3 days after the filter switch. I took the old filter and basically rinsed it out in the water and let the new filter suck it all up.
Fast forward 3 weeks later im out of town for work and my girlfriend calls and said we have dead fish.... She said the other ones are up at the very surface of the water and look like they are gasping for air. I told her to do a 50% water change instantly so she hooked everything up and did the water change. She said within 5 minutes of the water change the fish were back to acting completely normal.

I cant give you water test numbers because she doesnt know how to use the kit and im 800 miles from home. Is it possible that because the filter is pushing out water below the surface the oxygen is running out of the water?

The other weird thing she told me was we have 2 plants that are completely dead now and one that we had in the middle has quadrupled in size. Basically to the point where she trimmed over half of it and said its still the biggest plant in the tank. Could this plant be causing the issues?

I wish i could give more info but i wont be home until saturday and im hoping thats all it was and she can keep my other fish alive until i get home. I had her raise the filter output to where about 1/4 of it is sticking out of the water and she said its making really big ripples at the top of the water now and bubbling.

This pretty much sucks cause im sitting in a hotel room with nothing to do except think about wth happened to my fish.

 

[Robin]

Is it possible that because the filter is pushing out water below the surface the oxygen is running out of the water?

No that's definitely not it.

My guess is that your new filter was not cycled properly and your fish were reacting to either high ammonia or nitrite. Testing a few days after the installation of the new filter wouldn't have shown there was a problem because it takes longer than that for the ammonia to build up.
Rinsing the old filter out in the tank wouldn't have transferred enough of the beneficial bacteria to seed the new filter.
Next time what you should do is to leave the old filter running on the tank while the new filter gradually takes over. Three to four weeks should be long enough.
Your girlfriend should do daily or every other day partial water changes with a good quality declorinator. Ask her to check and make sure there's a good strong flow coming out of the filter return. Also: have her add 1-2 teaspoons of salt per ten gallons, (sodium chloride without any additives). This will help to detoxify any nitrite.

Sorry you lost the fish but you saved the rest by knowing to do a partial water change.

Robin