Ammonia Spike?


New Member
I have a 40 gallon breeder saltwater fowlr tank. A couple days ago I saw an ammonia reading of around .18 after determining my fish acting strangely. I did a full water change immediately and the readings seem back to normal. My stocking is fairly small:
1 cleaner shrimp
1 snail (unknown kind, he was a hitchhiker on a rock)
1 clownfish
1 flame angel
1 yellow tail blue damsel

I was only 2 days behind on my 50% monthly water change, so I don't believe that was the problem. I was hoping you guys could help me determine what might have caused it. Thanks.


Hey! How long has the tank been running for?

I think there are three possibilities,

1) faulty test kit (unlikely as you said fish was acting weird too)

2) something died (whether this be a fish, snail, macroalgae)

3) the tank hasn't been cycled properly and it's a relatively new tank (couple months old)

Any ideas which you think could apply to you?


New Member
Thanks for replying!
The tank has been up (starting from the conclusion of the first cycle) for about 2 and 1/2 months so that third possibility seems the most likely. The API test kit is brand new and has been used pretty reliably on other tanks, and nothing has died (though algae might be a possibility). The tank was fully cycled without fish for about 5ish weeks.

Although this is my first saltwater tank, I have done freshwater for many years and the only time an ammonia spike was due to overfeeding/fish loss.

Are ammonia spikes common in tanks that have already been cycled but are still relatively new?


Your tanks been running longer than mine! I've been freshwater keeping for many years but I just got into saltwater in September.

I added fish slowly, so there was no ammonia spike after the first one went away.

So you set up the tank 2.5months ago post cycle. How quickly did you add then 4 large livestock? It maybe that they were added faster than the bacterial load could cope. In which case it should catch up soon and you shouldn't get any more spikes


Active Member
My guess is you already did a WC and retested your water. If all good then I agree with Shilpan's statement above if Amm. was higher then something died. Your tank is still new and will take awhile for it to mature it will take to small changes but not big ones. It took my tank 3.5 months before the nitrite zeroed added two small clowns couple hours ago :D. My .02 research and ask questions Good Luck...