Nitrite And Nitrate Spike - Why!?

[pezzah]

A few months ago I bought an established tank from someone along with a whole load of fish. In a manic day we got it home all set up and running. I tested the water every day at first and everything seemed to be working well with little or no amonia or nitrite and gradually rising nitrate. I do 20-25% water changes every 7-10 days to keep the nitrate down.

However, this weekend the nitrite and nitrate have both gone through the roof, I did a 50% water change yesterday and today nitrite is back to over 1mg/l and nitrate is between 50 and 100 mg/l but amonia remains low. The PH of the tank seems about right, about 8.0 I think.

I haven't changed anything in the filter, just washed the sponges in tank water and replaced 1 of 4 sponges weeks ago.

The tank is 180 litres (Juwel 180) probably a bit overstocked with 7 clown loaches, 1 kissing gourami, 1 yellow gourami (can't remember its proper name!) 8 tetras, 1 red tailed shark form, 1 pleco, and 3 other fish which I'm not sure what they are! In general the fish aren't looking to happy at the moment, not swimming around much and not eating as they normal would.

There's a few plants in the tank which aren't too healthy at the moment.


Can anyone give any reasons/explain why the nitrite and nitrate are going to high?


Thanks,

Andy

 

[aaronnorth]

rotting plants release ammonia.

 

[WILDER]

Your tanks overstocked.
Clown loaches need 100 gallons as they get bigger.
How often do you do a gravel vac as plecs are massive waste producers.

I would add another filter to the tank squeezing some beneifcal bacteria onto the new sponges, off the old sponges.
We the sponges first in tank water.

 

[pezzah]

I gravel vac with every water change, so once a week or so. I'm reluctant to buy another filter as up until now I've had no problems so I think the filter should be able to handle it.
The clown loaches are still quite young I think and I may well pass them on to someone else once they get too big!

I'll remove some of the worst looking plants and see if that helps. Any other suggestions?

 

[WILDER]

I would remove the rotting plants.
Juwels filters are not that good and it best to over filter a tank anyway.