View Full Version : Big wc at the end of cycle ??? Help

08/09/2017, 07:58 AM
Hey everyone, so I think I'm to just about the end of my cycle , my ammonia is zero, my nitrites are at zero, and have been so for about 3 weeks, my nitrates however have been at over 64 ppm for the same amount of time, I've been doing bi -weekly 5% water changes,, and nothing seems to have changed my nitrates, my biopellets are online and have been for a while, am I missing something ? I used brs reef saver rock, with sump I'm at about 110 gallons of water (+/-) and I have about 60-70lbs of rock in there , kind of a minimalist aquascape ,, I started my cycle at the first of June like 6/6 I think ,, why is my nitrates so high ? Am I missing something ? Do I just need to do a giant 80% water change?
Please share your input with me guys

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Vinny Kreyling
08/09/2017, 08:02 AM
Could just be the water changes.
If I understand biology any interruption in a cycle will in turn slow it down.
Let nature resolve it on its own.
But there is also the possibility that I am all wet.

08/09/2017, 08:15 AM
The denitrifying bacteria are the last, and by far the slowest to grow. You could go for 6 or more months before you tank is able to maintain very low nitrates, depending on your setup. I see you have biopellets, which will help. the bacteria still need to grow though. Biopellets just give them enough "food" to grow, as carbon is generally the limiting factor in their growth in an aquarium.

They also only grow in low oxygen areas, like inside of live rock, or in a deep sand bed. If you don't have a deep sand bed, or much live rock than you may have issues getting enough to grow to maintain low nitrates, even with carbon dosing or biopellets. You can always add biospira, or matrix to your sump to increase the area they have to colonize. Also, man made live rock is usually much less porous, so less effective at growing this bacteria.

With numbers so high, I'd probably do a large water change until you get down to 40ppm or so, then just keep an eye on it. Nitrates generally don't bother fish much, but coral will suffer from high levels. With having only had your tank setup for 2 months, I'm not surprised you have high nitrates. Shouldn't cause alarm at this point.

08/09/2017, 01:16 PM
I agree that the nitrate-consuming bacteria seem to be the slowest to get going. A few 15-20% water changes might be useful to remove some nitrate and other secondary metabolites, though. I'd also get a second opinion on the nitrate test kit, since they do fail from time to time. 64 ppm is high but within the expected range, so I wouldn't worry much.

You can do larger water changes, but I would avoid exposing the live rock to air, since that can kill organisms.