Will medium-high nitrates stall cycle?

[twintanks]

What a week...crashed computer (I'm on a borrowed one) and now possibly a fishless cycle problem as well. I was going to move my fish immediately into a new 5 foot tank, from their old one, along with all current filter media; but for reasons too complicated to put on here, I am now doing a fishless cycle on the new tank.
It's now on Day 17 and seems to be going ok, but I am a little worried that the nitrite-eating bacteria might be rather slow to get going. The new pump has been seeded from the existing one with sponge material and Biomax, also I've added quite a bit of gravel from the current tank onto the floor of the new one. No plants; no ornaments; temperature 24-25 degreesC.
I have reached the "ammonia snack" stage. I have 0-0.25ppm ammonia and 2+, maybe 5+ ppm nitrites (nitrites have been rising since day 8). The snack dose ammonia was reduced from 1ppm to the present readings in about 48 hours; leaving the tank still with high nitrites and now also nitrates between 40 and 80ppm.

The last two cycles I ever carried out on tanks never showed any nitrite, so this is new to me. Since there's still a lot of nitrite to process, is it possible for the nitrates to adversely affect the cycle?
I'll be approaching zero ammonia again very soon and the guide-notes suggest only one "snack" dose. My first thought is to do a water change, to reduce the nitrates (and also nitrites), because more ammonia additions (snacks) means more nitrite, etc.

Anyone got any thoughts? What would be a good level, in terms of ppm, to reduce the nitrites and nitrates to, via water change?
Sorry for the ramble...

 

[twintanks]

Just found the May 22nd post from John Bennett titled Fishless Cycling, looks like he had a similar problem, so I'm going to do a big water change and try and balance the books from there...

 

[Gruntle]

I don't know for sure, but as far as I can tell from my experience, high nitrates (and I got to over 160ppm on one tank) didn't affect my cycles.

 

[twintanks]

Thanks for that one, Gruntle, useful to know what other people have seen with nitrates. Well, last night I did a 30% change (give or take a few pints) and this morning the nitrates are around the 40 mark, with nitrites somewhere around 2...the tube doesn't look quite as strong a psychedelic violet as it did last night. I'm going to let it all run today (the ammonia is zero) and then look at it all tomorrow morning....it'll need a tiny ammonia snack dose again at some point but it was interesting to read on the other thread I mentioned, that the ammonia-eaters can go along for some time without being fed. I'd like to get the nitrites down closer to 1 before I do that, though.

 

[StevenF]

One thing to keep in mind is that the beneficial bacteria don't just need ammonia or nitrite to live and grow. They also need phosphate, potassium, sodium, calcium, sulfur and and a lot more for growth. It is often assumed the your tap water will have all of these except nitrite and ammonia. However the bacteria growth may stop if a nutrient deficiency does develop. Doing a water change would help if this occurs. It may or may not be the nitrates causing the issue.

For example take a container of RO, distilled, or DI water and try to cycle it by just adding ammonia. It will not work. It will just sit there and gradually the ammonia and water will evaporate.

 

[eaglesaquarium]

The issue with large nitrate numbers is that it can cause a pH crash at times once the buffering capacity of the kH has been reached. The kH is really the measure of the carbonate... and the bacteria need the inorganic carbon. So, that's why high nitrates can be a problem. Generally a water change during a cycle isn't a 'bad' thing. It might slow you down a bit (the more ammonia or nitrite present the faster it will go - up to a point), but if things are already slowed... where's the harm?

As with keeping the fish healthy, sometimes a nice big water change is truly the best course of action. In this case, I'd suggest doing the water change and not worrying about it. It will all be back in gear again very shortly there after. And since you are removing a large chunk of nitrite, it might actually take less time.

 

[StevenF]

The issue with large nitrate numbers is that it can cause a pH crash at times once the buffering capacity of the kH has been reached. The kH is really the measure of the carbonate... and the bacteria need the inorganic
carbon.

A PH crash is a strong indication of no or low potassium, calcium and magnesium levels. All of which bacteria need. You cannot get a PH or KH crash if potassium, calcium and magnesium levels are sufficient for bacteria growth.

 

[twintanks]

I have fairly hard water so nutrients should be there. Just reached dose 4 in the instructions...the ammonia level drops well (but not yet to zero in 24hrs), nitrites likewise...they,re readable (currently about 2+). But it seems to be going OK since the water change so hopefully it won't be much longer...

 

[StevenF]

I have fairly hard water so nutrients should be there.

Hard water is no guarantee everything is there. It;s less likely with hard water but still possible. But it is good to hear the water change helped.