Originally Posted by Canuck Fins
While doing a fishless cycle, if I need to add a bit more water (maybe a litre) to the tank (5g, heated, filtered), do I need to worry about water conditioner?
And in general, how high does ammonia spike before the nitrites start showing on the test?
Err on the side of caution and add the conditioner. There just might be enough chlorine or chloramine in there (though diluted by the conditioned chlorine/chloramine free tank water) to kill or retard the growth of beneficial bacteria thus slowing down the time to cycle your tank. This is for tap water, if you're using bottled water, you don't need to condition it.
No one really notes how high their ammonia spike gets up to, but I've read around the web that you want to keep ammonia to 5ppm level for the first two weeks. Even adding more ammonia to keep it at that level since it gets used up by the growing bacteria. I've seen a graph where someone was cycling their cichlid tank and it went up to a peak of 20ppm (spike peak at 10 days) for ammonia and 50ppm for nitrites (appears at 2 weeks, spike peak at 30 days).
Here's the link with the graph about 2/3 of the way down the page. It's a really good read as well if you want to read up on the cycling process.