Nitrates too high at end of cycle?

[nphsmith]

First time tank owner, in theory my daughter's .

We currently have 250Mg/l of Nitrates, if I read our tester right. This seems extremely high. We have a 78 litre tank, and introduced fish 3 weeks ago (6 Dorios, 2 small Corys, 2 platys, 3 harlequins).

Our Ammonia level peaked at 3-4, and is now down to 0.5, which seems right. We had to go away for 3 days and put in a crumbly pyramid feeder, which kept them alive but I worry may have overfed them.

Nitrites also seem a bit high, at 5Mgs.

I have done 2 10% water changes, one a week ago, one today.

Should I be doing a big water change at the end of my cycle? Should I be doing it now or wait until Ammonia is down to zero? And how big should 'big' be?

 

[fort384]

Welcome to AA!

You should be changing water as much as required to keep the ammonia and nitrite below 0.25ppm, and keep the nitrate down to 40ppm or less. 50% at a time is just fine for a PWC, so long as you treat with a dechlorinator like prime, and match temperature reasonably close. With nitrites that high, your fish probably won't survive much longer... nitrite is even more toxic to fish than ammonia.

Take a look at this thread... it will help answer some questions and shed some light on cycling a new tank with fish:
http://www.aquariumadvice.com/forum...ady-have-fish-what-now-116287.html#post983258

 

[nphsmith]

Firstly, thanks very much for your response.

On one of the threads I read last night, it suggested that paper strip tests were not reliable, so I have gone and invested in seperate liquid tests, which give what look like more likely numbers:
PH>7.6
Ammonia down to 0.25ppm
Nitrite 5 ppm
Nitrate ~60ppm

According to this site:

Beginner FAQ: The Nitrogen Cycle

I should expect Nitrites to rocket as Ammonia decreases, and then descend as the Nitrates peak. Is that right? Also the PPMs seem much higher than you are suggesting is safe?

I'm going to do a 2 bucket (20%) change now, which presumably brings down NO2 and NO3, but should I be worried that that may disrupt the cycle?

 

[fort384]

PWCs will not disrupt the cycle. You are right about first seeing Nitrites spike (which you have right now) and then the nitrate will spike even higher. With your test results, I would say you are on the downhill part of the cycle... but you still need to do a few massive water changes over the next few days to get that nitrite WAY down. 50% or even more at a time is just fine...

 

[nphsmith]

Thanks for your feedback. Wrote a long post but forum gremlins nabbed it. Anyways, have now done a 40-50% water change, *and* got some liquid testers as opposed to the dry strip ones whose colours I could barely tell apart!

A little confused as this site : Beginner FAQ: The Nitrogen Cycle suggests Nitrites will go quite high as part of the cycling process anyway?

 

[nphsmith]

Meh! Please disregard previous post, didn't realise it was moderated!

 

[nphsmith]

OK, I ended up doing ~40% water change last night and around ~50% tonight.
Being almost completely colour unaware, I've let the girls tell me the test results, and they say Nitrate is down to 10ppm, Ammonia to 0, which is great, but Nitrites still at 5.

Which means one of a few things:
1) Water changes are removing nothing by way of Nitrites (I tested before and after the 50% water change and they claim 5ppm for both). This seems mathematically impossible.
2) There are Nitrites in the tap water, which I'm fairly sure not, as it took a couple of weeks for Nitrites to show up.
3) The actual Nitrite level was much higher than 5 previously, and is now down to 5. The test colour looks lighter to me for sure.

So I *think* I'm on the right path. Presumably I test again tomorrow and do another big change if Nitrites remain at 5? Shouldn't I reach a point at which the bacteria are capable of turning all Nitrites to Nitrates without my intervention?

 

[fort384]

You are on the right path... if there is no nitrite in the tap water, and you do a 50% water change, your nitrite will be reduced by half. Do another PWC soon...

And yes, once the cycle is complete, you will have sufficient nitrosoma bacteria to convert nitrite to nitrate.