Water change during cycle?

Nah, the cycle will go on and on and on forever and ever. It'll hit equilibrium and your numbers will zero out. Every time you do anything (add or remove) the equilibrium has to be reestablished - we call that a mini-cycle and is why we wait between adding fishies, etc.

But to the point of your question, yes, once you hit all 0's you're good; but you may not zero out on your nitrate.... IMO, once Ammonia/Nitrite are 0 and your Nitrate is dropping (and lower than 20) that's when you're ready for your next step (for me, next step was clean up crew).

 

I'm going to disagree with some things on this thread. ;D

This is something that has been spread over the internet, magazines, books, etc. since I can remember. There's only one problem......it's wrong. Not doing a water change can lengthen your cycle, not extend it.

If I get just a small spike of Ammonia I tend to let nature take it's course. However, if I get a large spike of Ammonia, I do a large waterchange immediately. One reason is quite simple to understand. A high Ammonia level actually causes Ammonia to go up and not down. That's because the high level is killing worms, featherdusters, snails, and other LR hitchhikers.

If you can measure Ammonia, it means one thing.....the bacterial population is not in equilibrium with the quantity of Ammonia. Here's a few other things that are often discussed, the higher the Ammonia you get in your initial cycle, the more stable your tank will be. Unfortunately, that's wrong too.....bacterial populations are highly dynamic. If there's Ammonia present, their populations can grow very quickly. Once that source of Ammonia is gone, the bacterial population will quickly go dormant and then die unless a new source of Ammonia is not added.

Additionally, high levels of Ammonia actually has a negative impact on the reproduction rate of Nitrite Oxidizing Bacteria so your Nitrite spike will last longer. Note that this microbe is actually Nitrospira and NOT Nitrobacter as you probably have in your books on reefkeeping. Nitrospira - MicrobeWiki Less Ammonia means that you will have a smaller Nitrite spike and in this way, you'll have a shorter cycle.

 

Hey! Thanks great info!

 

+1 and K+ to you. I've always thought this myself, but never posted this on a forum for fear of being tarred and feathered.

I did two water changes to prevent excess die-off during my last cycle (to help the bacteria along, if you will) and the cycle only lasted about 10 days or so (at 10 days I was down to zero ammonia, zero nitrates, and 5-10 nitrates.) A couple of weeks later, I'm still at zero ammonia, zero nitrites so I know for sure the bacteria population is there.

Oh yeah, and I ran my skimmer as well.

 

LOL We rarely, if ever, do that.