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Cycling Aquarium with Cory's Method

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I am setting up a tank in which I plan to breed guppies...this will be my fourth tank, but the first that I have attempted to cycle using Cory's method as laid out in this video:

Cycling a Planted Aquarium Biological Filter

So, my question here is how do I know when it is safe to add fish?

My understanding is that the gross algae growing everywhere will be able to take care of any ammonia/nitrite/nitrate spikes from adding fish gradually, and as the fish eat the algae, and you adjust the feeding of the tank down to only the level of the plants you want to keep, as the algae levels settle down the beneficial bacteria will catch up, thereby achieving a "cycled" tank without seeing the typical indicators.

Is this a correct understanding?  If the tank is all gross and algae covered, does that mean it is now time to toss in some guppies?


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I tried this method in a quarantine tub, and my water sprite was already sprouting tons of new leaves by week 1 so I figured it was safe to add fish. However, I ended up getting an ammonia spike a couple of weeks later. From now on, I plan to wait till my plants/algae have been growing for at least 3-4 weeks before adding fish. The greater the plant/algae mass, the more likely it'll be able to handle fish. 👍

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Ok, thanks.

I'll try putting in fish shortly...it's been going for 4 weeks now, and is absolutely gross with algae (and copepods that hitchhiked in with the hairgrass...will try to save some of them for the baby guppies, but we'll see)

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I feel one important step is to slowly increase  the fish over time. Each fish adds more load and the bacteria will  have a lag time. I personally cycle  my tanks from start with  fish. I use 1-3 nano fish depending  in the size of the tank and I just test the water almost daily and feed sparingly.

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