Has my tank cycled?

[RaymondNoodles]

Hello! My 20g Waterbox tank has been running for almost 3 weeks. I started with very seasoned wet live rock that I got from a running tank with all sorts of interesting things growing/living in/on it. It had a decent amount of green algae on it, and looking back I think I should have scrubbed most of it off, but I left it au-naturale. I did a 20% water change after 1 week. All levels have been perfect and water has remained crystal clear. I added a cleaner shrimp, emerald crab and and turbo snail after the first water change and everything is doing well. Getting a little detritus in the sand and small amounts of brown algae on the glass here and there but nothing that seems bad. The algae that came on the live rock has significantly diminished. The shrimp, crab and snail are all very lively and eating great.

Ammonia spiked to between .25 and .5ppm right before the first water change but has been between 0-.25ppm for the last week. Nitrites never went above 0 and nitrates have been between 0-5ppm but closer to 0. Salinity steady at 1.025. PH steady at 8.1. From what I have been reading, it's possible for a tank to "immediately cycle" and I am wondering if you all think that has happened. When do you think we should be safe to add a clownfish? Thanks!

[seabass]

Establishing the nitrogen cycle doesn't require an ammonia spike.  If there was enough bacteria on the rocks to process the ammonia being produced, you won't be able to detect any ammonia.

 

However, the fact that ammonia reached 0.5ppm means there was either a lot of die off on the rocks, or there wasn't enough bacteria present.  I'd give it a couple more weeks before you add a clownfish.

[rough eye]

you shouldn't do any water changes until after you're sure the tank has cycled, unless there is some extreme emergency.

[RaymondNoodles]

22 hours ago, seabass said:

Establishing the nitrogen cycle doesn't require an ammonia spike.  If there was enough bacteria on the rocks to process the ammonia being produced, you won't be able to detect any ammonia.

 

However, the fact that ammonia reached 0.5ppm means there was either a lot of die off on the rocks, or there wasn't enough bacteria present.  I'd give it a couple more weeks before you add a clownfish.

I probably shouldn't have added the shrimp, crab and snail so soon. I am not the most patient person 😬 I do have thriving corals and other organisms some might call pests...if it's any constellation. Thank you for the input.