How long to cycle the tank before putting in fish?

tonggao

New member
I have a newly setup 120G tank with about 100lb of live rocks (have been cooked for 2 months), and only have new saltwater in it for about a week. With the current situation, I need to move about 8 fish either to this new tank or another established tank. I prefer to move them to new tank since it is less stress for the fish and me to just move them once, and my other tank might not be big enough. Is it safe to put fish in the tank after only cycling for one week? Since the rocks have been fully cooked, it should not have any bad peak or algea bloom, right? Is this enough time for bacterias to establish equilibrium? Thanks.
 
Any new/old sand?? If not I say it's ready. If you want to be sure, wait for another week and test the water.
 
I have about 5 inch of sand in fuge that I pulled out my other tanks, and I washed them many times before putting in this tank. So the sand is clean and very dead.
 
I would say a week is not long enough for the nitrogen cycle to complete or be at levels safe enough for fish. Everything in your new tank is pretty much new. IMO I would wait at least a month. Unless your ammonia and nitrite levels are at zero prior to that.
 
What are your readings? If ammo/nitrate are 0, maybe you're cycled. But if a lot of fish hit that tank at once, there's a good chance of bumping the ammo/nitrate back up into the 20's.
 
Read up on fishless cycling.

Basically you dose the tank with an ammonia souce, and turn up the temps to high 80's to build up your nitrogen cycle bacteria very quickly.

I've brought up a tank in less than 2 weeks that way.

You can use ammonium chloride, household ammonia, even ammonium nitrate which is what was convenient for me to use the last time.

Ammonium nitrate is the chemical inside the instant cold packs. Shhh... don't tell any terrorists :)

I'd still be concerned about putting a bunch of fish in at once though.
 
I would agree a week isn't long enough for the nitrogen cycle to have lapsed. If the rock is really cooked and the sand is essentially sterile I don't really see any way for bacteria to have built up to cycle the tank.

Been a long time since I cycled a tank though but I am pretty sure you need some sort of bioload in the tank.

I wouldn't risk eight fish on it.
 
Thanks everyone for your advices. You are right that I should not risk my beloved fish, and I will put them in my other tank for now if I have to move them. Funny thing a couple of weeks ago i twisted my ankle, and found out that the instant cold pack is made of ammonium nitrate and water (I was pretty excited about the finding at that time:) ) like Norman said. Do you have a web link to your method? How much ammonium nitrate should I use? Will the ammonium nitrate hurt the live rock and critters in them? Thanks again.
 
Don't have a link for ammonium nitrate method.

I read up on the ammonium chloride method, and just figured out the corresponding amount of ammonium nitrate to use, based on the molecular weights.

I didn't have any problems with live rock, live sand, or pods when I fishless cycled. Basically with the ammonium nitrate method, you have your ammonia source, and the nitrate give you.... well, extra nitrates... which is where the ammonia goes anyway.

When cycling, you look at the spike in ammonia levels, followed by the spike in nitrite. Watch for nitrite to drop off, and you'll see nitrates go up.

When the nitrites go to zero, and everything seems to stabilize, you can do a few big water changes to bring down the nitrate levels. Then you're good to go, and can start slowly stocking.

Oh! And remember to turn down the heater if you've cranked it up to 88 degrees or something for the bacteria.
 
hmm cooked rock doesnt contain enough bacteria? i'm curious on this topic as I am about to upgrade from my 38 to 120. Sorry to hijack the thread tonggao
 
No problem Simon, and I am actually wondering the same. I just measured the water, and it has 0 amomnia, 0 nitrite, and almost 0 nitrate before adding some ammonium nitrate. I guess I have either a very muture system or a very new system. How can I tell? I am thinking about measuring it again in a couple of days, and if everything goes back to 0 (after adding ammonium nitrate), I can conclude that I have a mature system. Otherwise, I should wait for the whole cycle to complete. Is this reasonable?
 
There are people doing 100% water change. So when they do that they have to wait for it to cycle again?? I wouldn't add all the fish at once but I think you can add one or two. Pick the one you hate the most :lol: ..
 
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