Hi all
i have had my 72 litre tank set up for a few months now. I cycled it with ammonia and added fish about three weeks ago (6 black neons and 2 otos). all was going well excpet for my nitrate levels which were high due to high levels in my tap water. I bought a nitrate filter and have being doing water changes the last few days to sort this out. The filter brings my nitrates down to 0-5 from 40-80.
I did a water change today and then afterwards checked my ammonia, nitrite and nitrate levels. Nitrite is 0, nitrate 20 but for some reason ammonia has jumped to 1-2! I have no idea why.
I havent added any new fish. My tap water has 0 ammonia and after running it through the filter it is still 0. I did clean the filter a few days ago but washed out the white sponged with aquarium water and replaced them and changed the polywool (I have a fluval u3). The only thing I did add today was some plant fertiliser as some of my plants are looking a bit brown. This was Love fish plant fertiliser.
Any idea why the sudden spike and what I should do about it?
I havent added any more fish since the original ones three weeks ago and things had been stable since adding them.
Thanks for the help!

Which dechlorinator do you use?

Hhmmm odd. I have just re-tested the ammonia and it is now back to normal! I can only assume that the test tube was somehow contaminated with ammonia. Now that I think about it my partner had put all my test kits in a bag today along with the bottle of ammonia and the syringe I was using to dose the tank. Maybe this somehow contaminated it? I cant think of any other explanation for the result?

Tetra aqua safe. I added it to the water mixed it round then added the water straight to the tank. Could that have had something to do with it if i didnt wait long enough for the aqua safe to work?

No, it doesn't take long to work. Can you check the label and see if it treats chloramine as well as chlorine? Some older stock is still on sale that only treats chlorine and that may be a factor.

Yes it says on the label it does both.

OK, well if your water supplier treats with chloramine, the way the dechlorinator works is to break the chemical bond between the components, releasing chlorine, which is treated in the usual way, and ammonia, which will be processed by the filter eventually. However, 1-2ppm sounds like a lot. If you have difficulty distinguishing the colours, it's probably at the lower end of what you're seeing. Similarly with tap nitrates, actually, as if it was 80ppm you could prosecute your supplier as that level would be illegal.

I would retest and check to see how well the filter is dealing with it. If it's rapidly reverting back to 0, then the problem is likely to be chloramine based. If it does not rapidly reduce there must be another factor at work which has either compromised the filter bacteria, or there is a source of ammonia somewhere in the tank - decaying organic matter, a dead fish etc. Are all fish present and correct? Is there any excess food lying around or buried in the gravel? How bad is the plant decay? Are there lots of dying leaves?

Thanks for the advice.
My ammonia is now reading between 0-0.25. I always have trouble distinguishing between those two. I guess that must mean it was related to the dechlorinator as its dropped so quickly?
I also have trouble distinguishing between the nitrates but my tap water always comes out more redder than orange which I take to be a bad thing (using the nitrate filter its a nice yellow). Since doing a few water changes with this filtered water its looking more orange after doing a test. I will do a few more changes over the next couple of days to get it as low as possible.
I do have a fair few brown leaves on the plants. Is it best to remove these rather than just letting them decay in the tank?

Yes it's better to take them out - if they rot in the tank they will produce additional ammonia which can put a strain on the filter, especially in a new set up.

Out of interest how much harm does it do to the fish adding the dechlorinated water. I guess its less harmful than not treating the water first but surely adding small amounts of ammonia created as a byproduct of how the dechlorinator works must be bad?
That said I guess there is always some waste floating around in there produced by the fish which contains ammonia so it cant be that bad?