First Cycle on New Tank


New member
Greetings All,

Simply looking for a few words of advice as well as some help for others when completing the first cycle. There are a lot of posts about "starting the first cycle", however I've not been able to find many posts about what to expect when cycling the tank.

During your first cycle, what do you expect to see throughout the 3 to 4 week cycling period, depending on your setup?
What types of growth is one looking for? Good Growth verses bad growth?
If testing towards the middle / end of your cycle, what do you expect to see?


New member
It's really pretty simple. Ammonia will spike, then nitrite will spike, then nitrate. Length of time depends on a lot of factors, mainly if you've seeded the tank with any live bacteria. I'm assuming you either started with live rock, or added pure ammonia to start the cycle

You'll probably see a diatom bloom, it's natural and should go away relatively quickly. Other than that a cycle without live rock will look pretty bare. If you have live rock you might see some hitchikers open up.

Testing wise, you're waiting for the Nitrates to go down. Be patient! Once you see the ammonia spike and fall it's just a waiting game.


New member
To get the cycle started off, either put a piece of raw shrimp in the tank and let it decompose, or ghost feed(pretend like there's fish in the tank, and feed a bit of pelletes/flakes every day) Take ammonia readings, and if you see a spike, then you'll know your cycle as started. You can take out the decomposing shrimp if the smell gets too bad and your getting an ammonia spike. Next thing to spike will be nitrites, and then finally nitrates. Once you see the nitrates spike, and the ammonia + nitrites at approx 0, do a water change. Then let the tank sit for another week or so, and make sure the nitrites and ammonia is down to 0. If the nitrates are still a little high, feel free to do another water change. At some point towards the end, you should see a diatom bloom, which is good. At that point if the water params are good feel free to start adding some clean up crew.(snails/crabs) Add a few at a time to start to make sure you can sustain them. Then work your way up to fish and such. Good luck!


New member
Thank you both for the information. Watched the diatom bloom at day 7, and now we are getting rid of some red algae and little air bubles we believe to be bad at the moment. From what my wife and I found on RC forums, a blackout should do the trick, espicially since we've got nothing else in the tank.

It's just interesting to watch things grow and flow. Wasn't sure what was good to be seen and what wasn't good.

Also, started the cycling with uncured live rock so I know that adds some time.

Justin, we ended up with a hermit crab and the Wife found out the crab could grow and eventually sting the fish, so we pulled him out. He just magically appeared one day.


New member
FYI, the air bubbles aren't in themselves necessarily bad. It's probably just nitrogen being given off by the algae and things in your tank. Mine did that for almost 4 months after I set up my tank. Even now (6 months in) I've still got a bit.


Professional amateur
and now we are getting rid of some red algae and little air bubles we believe to be bad at the moment. From what my wife and I found on RC forums, a blackout should do the trick, espicially since we've got nothing else in the tank.

Or you could let it go for a bit since it's a new tank. While algae indicates an "excess" of bad nutrients that's too be expected in a new setup. As you add life and the tank matures these things tend to even them selves out. Now if the algae looks like it's about to smother the tank then yes do something about it. If it's just some tufts here and there they can be fun to watch and it's a good experience to see how the "life" in the tank behaves. I let my algae grow and then as I got my fuge up and running it was fun to watch it wither away on it's own as the fuge started doing it's job of sucking up the "excess" nutrients.

Oh and if (or when) you add a CUC you'll want something for them to eat. So some algae can be a good thing.


New member
Thank you for the advice, we uncovered the tank and let it do it's thing. Probably adding 1 CUC this weekend, depends on the levels.

We're running this without any type of fuge, just a HOB filter with a Pura filtration pad. LR and LS. I expect algea to grow at some point and will be putting in a plant to somewhat counter it. but that's down the line a little bit.

So while the main 10g is cycling, we should also be cycling our QT tank as well?

From the looks of it everyone recommends QT'ing the fish before they're entered into the MT, even in a new tank as to prevent ICK from developing in the sand.