Early Morning emergency


30 Jun 2018
Newcastle upon Tyne
Hi all,
Nice bit of drama before leaving for work this morning.
All of the fish were pretty stationary near the top of the tank and the water appeared a bit cloudy. The MTS were also hanging around the top of the tank.
All things considered this was a bit strange so I did a quick water test and I had both Nitrate and Nitrite present! I did a quick 70% water change and things seemed to be getting back to normal.

I'm pretty sure the cause of the Nitrite spike is that I put some steamed vegetables in last night for the fish to eat. 2 pieces of broccoli and 2 slices of carrot. I have fed these before but not together.

On reflection this morning there was a strong aroma of cooked broccoli lingering but I thought that was the wife!

Couple of questions if anyone can answer:
  • Will my filter media have been damaged by the nitrite spike?
  • Previously I've mainly boiled veg before adding to the tank. Has steaming changed the rate of decay?
Thanks in advance,

Simon Cole

25 Dec 2018
Hi Nick. You filter will not be damaged by nitrite. Boiled broccoli does have that smell and will certainly decay faster than fresh. The tests kits are often inaccurate and nitrate is harmless in aquarium concentrations. MTS always climb up the tank overnight and many fish sit at the top in the morning. I would be worried about nitrite, but it seems more probable that oxygen was slightly depleted due to a change in COD caused by boiled vegetable organics entering the water. It is only a hypothetical situation and is not something I have observed before, so I would go to work happy. Most water conditioners have some ability to detoxify nitrites. If you were worried about the organic load then you don't need to be once the water has been changed.
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