Ammonia probs

I have a 300l tank which is (was) cyled months ago, Ammonia and Nitrite both at 0 and Nitrates 40ish. It's been that way for months and I hadn't checked the water for a few weeks. I went away for the weekend and came back to find that the DayLite tube had gone while away and the plants were suffering.

It took me a few days to get hold of a new tube and then I tested the water to find that the ammonia was 4ppm, Nitrites were 0 and Nitrate was 60ish. I put it down to the plants having decayed and built up the ammonia.

I did a 50% water change and have been checking the ammonia every day, it's gone down after bi-daily 20% water changes and another 50% change today, it's now at 1ppm and tomorrow I should see the results of the 50% change.

What I am curious about is how can the ammonia build up so high and the nitrite stay at 0 ? I thought that the bacteria (which is already present because of the presence of Nitrates) doubles every 15 hours so I'd expect to see some Nitrites.

Anyway, I'll keep testing and doing water changes until it's back under control. I may have made the problem worse by being over zealous with the filter maintenance. I have 2 TetraTec cannister filters and at the weekly water change I take out all the media baskets and rinse them out in the water from the cannister (tank water). So I'll cut back on the cleaning of them I think.

Anyone any suggestions or comments? Apart from what's mentioned above, I haven't done anything out of the ordinary, no new fish although the Red Belly's are growing and eating more but gradually so I'd expect the filters to 'grow' with the increased bio load ??

Matt

Hi Matt,

Your ammonia problem could indeed be caused by rotting plants. I would also be worth checking that you don't have a dead fish in there. That won't do your water parameters any favours either. I'm not sure the filter cleaning would have really contributed to it since you used tank water.

With regard to you seeing ammonia, there are two types of bacteria in your tank that contribute to the nitrifying cycle. One that turns ammonia into nitrITE and one that turns nitrITE into nitrATE. Since you had an ammonia spike, it's likely that the former bacteria couldn't handle the additional load. However, they were still able to create enough nitRITE for the latter bacteria to handle. That's probably why you didn't see any nitRITE. If you hadn't done any water changes and left the high ammonia, you most likely would have seen a nitrITE spike after a few days.

However, since you did do water changes, the nitrITE to nitrATE bacteria was able to slowly adjust to the greater load.

Hope this makes some sense.

It does make sense, I've checked fairly thoroughly for any dead fish especially given the tanks inhabitants and I'm careful with the feeding (as regards removing uneaten food).

Hopefully the more frequent water changes will allow the nitrosomosas to catch up.

Cheers,

Matt

Cheers John, I think that's good advice. I'll leave them a little longer between cleanouts and do one at a time.

Did a 50% change on Saturday and checked yesterday lunchtime to find ammonia somewhere between 0.25 and 0.5 with 0 Nitrite.