Nitrite Spike after 2 months of stable tank

[mickitiffen]

My tank went thru a major cycle--lost 3 fish around Labor Day. Did 50% water changes over 4 days (2x day) and finally got the nitrites down.
Tank is 20 gallon Fresh
1 ghost knife fish
2 small catfish
1 pleco
1 parrot cichlid (died last night)

I had been testing the water weekly and all levels were fine. Was away for 2 days and noticed that the filter was running slow (It is an Eheim). It seems if I lift up the plastic cover thing that sits on top of the filament in the prefilter it runs better. Not sure if this is how it supposed to sit but seems to have better output from the filter if it is up a bit.
Tested the water and found nitrites high 5. Nitrate was also creeping up between 40 and 80. Had been stable for weeks. ph 6.8 Kh 80. Did a 50% water change last night and added Amquel and Novoaqua(1.5 tsp of each per bottle). This morning the cichlid was dead. Did another 50% change and added Amquel and Novoaqua. Temp is about 75. Ammonia was about .25 or .50 (hard to tell)

The nitrites were still high this a.m. before the 2nd water change. What might have caused a nitrite spike? Anything else I should be doing besides checking the water later and PWCs (how much--should I change each time).

 

[QTOFFER]

A few ?????
How often do you vac the gravel? What model Eheim do you have? When did you last rinse the filter, and did you try cleaning the impeller?

I'm questioning the gravel because your nitrates have been creeping up. Often, this is due to excess decomposing muck trapped in the gravel. Live plants love this mulm and help keep nitrates down significantly.

The presence of ammonia and nitrate suggest that there you either had a die-off of beneficial bacteria, or something is decomposing in the tank and/or filter. Low filter output can result in bacterial die-off - the bacteria need oxygenated water to thrive. Rinsing the filter media in tank water and cleaning the impeller dramatically improves flow. Do you have any snails or shrimp that may have died, causing the ammonia spike?

Some Eheims don't seat well if the media baskets aren't placed just so. That's why I'm asking what model you have.

 

[mickitiffen]

A few ????? ANSWERS IN ITALICS
How often do you vac the gravel? Whenever I change the water about 1x a month What model Eheim do you have? Eheim Ecco 2233 When did you last rinse the filter, and did you try cleaning the impeller? I did this in Sept.

I'm questioning the gravel because your nitrates have been creeping up. Often, this is due to excess decomposing muck trapped in the gravel. Live plants love this mulm and help keep nitrates down significantly. What is mulm? I have some live plants, many have sort of died off over time.

The presence of ammonia and nitrate suggest that there you either had a die-off of beneficial bacteria, or something is decomposing in the tank and/or filter. Low filter output can result in bacterial die-off - the bacteria need oxygenated water to thrive. Rinsing the filter media in tank water and cleaning the impeller dramatically improves flow. Do you have any snails or shrimp that may have died, causing the ammonia spike? No snails or shrimp

Some Eheims don't seat well if the media baskets aren't placed just so. That's why I'm asking what model you have.

Ecco 2233

I am a little afraid of the impeller cleaning. This is an inherited hobby... I was wondering about the little green cannister that sits in the tank (a prefilter) and how the plastic cover is supposed to rest on top of the filament. If I lift it a little (still attached) the flow greatly improves. What do you mean by seat well?

 

[QTOFFER]

Mulm is the very fine particulate stuff that remains in the gravel even after a good gravel vac. It's mostly decomposing food, fish poop, and plant matter. It's a natural fertilizer for live plants.

I forgot to mention that green strainer that's attached to the intake. Mine often gets clogged with dead leaves which seriously reduced filter output.

On my Eheim 2026, each of the media baskets has a small O-ring that lines up with the intake opening or the media basket directly above it. If I don't seat a basket or the lid properly on the O-ring below it, the pump doesn't work well. I'm not familiar with the 2233, but the Eheim website says that it has interlocking baskets that prevent water bypass. This sounds similar to my filter's basket construction.

When you lift up on the lid while the filter is running, you might cause the impeller to drop slightly. Perhaps there's some gunk build up in the impeller housing and lifting the lid somehow frees the impeller of this gunk. Again, I'm not familiar with your filter, but mine has an impeller cover that's attached with screws. I haven't had the need to clean my impeller yet, but it doesn't look like a complicated operation.

Are your levels still high?
Good luck.

 

[mickitiffen]

Nitrite Spike after Tank stable for 2 months

My Nitrites were 1.0 ppm this morning. I chgd the water 2x yesterday. I increased the flow of air on the air stone by adjusting the valve a little.

What I was referring was not the filter itself but rather the prefilter that sits inside the tank. About 2.5 " in diameter, green plastic. Has filament in it and a green ring with open pie slices that are open. When the green ring is flush with the filament it impedes the output flow. Maybe it is causing too much pressure on the intake prefilter? The ammonia was between 0 and 0.25. Nitrates were down last night about 40. I didn't feed the fish tonight. They seem to be swimming normally (i.e. not gasping at the top of the tank, which is what happened when I had the high nitrites before). Should I not feed them? I will think about the impeller cleaning but being not mechanical I worry about breaking things.