New tank Cycle issue...

[r_mcwaters3]

Hey everyone, its been a hot minute since I have done a tank cycle and might be stuck but I'm not sure. This is my first time doing a fishless cycle. Started by dosing Ammonia from Dr. Tims and added Microbacter XLM for a start base colony. The tank had 20 lb fiji pink live sand from caribsea, and dead base rock.

This process started 4/9/2025. Everything proceeded normally with the ammonia getting to about 1.5-2 on a salifert test kit. Two days later on 4/11/2025 the Nitrites showed up at about 1mg/l and I kept to the dosing schedule for ammonia per Dr. Tims. on 4/13/2025 Nitrites got over 4-5mg/l so I did a water change of 5 gallons per instructions and it went back down to about 2ppm.. The Nitrites kept popping up past 4-5mg/l so on 4/15/2025 I did another 5 gallons and added more ammonia drops per instructions. This was the last time I added ammonia.

Around this time I got sick with a stomach bug so let it ride till about 4/19/2025. the ammonia finally dropped on 4/19/2025 to 0.15 or less and I though I was done. Tested before a 50% water change of about 10 gallons.

At 1 a.m.

Ammonia-0
ph-8.0
Nitrites-2-5

Did a big water change of 10 and re tested at 5 pm this afternoon

Ammonia -0
Nitrites-2-5
Nitrates reading at 25 ish, color is floating between that and 50 so likely in the middle
Ph-8.0
salinity 1.026 or 35ppt with calibrated refractometer
Temp set in tank to 77F

My main question is the Nitrites they wont really come down and seems to be just hanging out, so in my head from that info the cycle isn't done yet. Is that right or am I just being overcautious? There is nothing in the tank living but I don't really want to introduce fish unless its the right time.

Second question is do I just wait for the Nitrites to drop and re-test with ammonia to make sure the tank is processing waste effectively?

Also if you got this far in the question I appreciate it its been a minute since I had a tank lol

 

[Dan_P]

Hey everyone, its been a hot minute since I have done a tank cycle and might be stuck but I'm not sure. This is my first time doing a fishless cycle. Started by dosing Ammonia from Dr. Tims and added Microbacter XLM for a start base colony. The tank had 20 lb fiji pink live sand from caribsea, and dead base rock.

This process started 4/9/2025. Everything proceeded normally with the ammonia getting to about 1.5-2 on a salifert test kit. Two days later on 4/11/2025 the Nitrites showed up at about 1mg/l and I kept to the dosing schedule for ammonia per Dr. Tims. on 4/13/2025 Nitrites got over 4-5mg/l so I did a water change of 5 gallons per instructions and it went back down to about 2ppm.. The Nitrites kept popping up past 4-5mg/l so on 4/15/2025 I did another 5 gallons and added more ammonia drops per instructions. This was the last time I added ammonia.

Around this time I got sick with a stomach bug so let it ride till about 4/19/2025. the ammonia finally dropped on 4/19/2025 to 0.15 or less and I though I was done. Tested before a 50% water change of about 10 gallons.

At 1 a.m.

Ammonia-0
ph-8.0
Nitrites-2-5

Did a big water change of 10 and re tested at 5 pm this afternoon

Ammonia -0
Nitrites-2-5
Nitrates reading at 25 ish, color is floating between that and 50 so likely in the middle
Ph-8.0
salinity 1.026 or 35ppt with calibrated refractometer
Temp set in tank to 77F

My main question is the Nitrites they wont really come down and seems to be just hanging out, so in my head from that info the cycle isn't done yet. Is that right or am I just being overcautious? There is nothing in the tank living but I don't really want to introduce fish unless its the right time.

Second question is do I just wait for the Nitrites to drop and re-test with ammonia to make sure the tank is processing waste effectively?

Also if you got this far in the question I appreciate it its been a minute since I had a tank lol

When the aquarium can consume 1-2 ppm ammonia in a day or two, the aquarium has sufficient nitrifying capacity, aka, it’s cycled. The establishment of nitrite removal capacity takes longer, but since nitrite is relatively harmless in saltwater, it seems most folks don’t wait for this to occur before adding livestock.

Other stuff:

You can add a little ammonia to bring up concentration, say to 0.5 ppm, to confirm the aquarium can remove it quickly.

How big is the aquarium? I don’t understand why nitrite is not lower after a water change.

Are you using a saltwater API kit?

If nitrite is present, the nitrate test will incorrectly read high, very high for some kits.

 

[r_mcwaters3]

sorry, I have a 20-gallon Innovative Marine tank. It's the 20 AIO long version. I have about 16-17 lbs of dry rock and 1 20lb bag of live sand that have all been in there since the cycle started.

For the test kits, I started with the API and moved to the Salifert. I use both, and both seem to read around 2 to 5

I did not realize that about the nitrate, I just figured if one was high, the other would naturally have to be high since it converts it.

As I type this, I forgot to mention I used rodi water from a new Icecap RODI I ordered before I started the tank with Red Sea Coral Pro salt, but I haven't tested the new water to see if I somehow introduced extra nitrate that way

 

[r_mcwaters3]

small but mighty update for anyone fighting this in the future. Nitrites came down

my best guess is either I introduced to much of the ammonia drop, introduced them to quickly, or the live sand held/had some material in it that spiked the ammonia without me realizing it. And to be fair had I waited a few more days without a water change it may have fixed itself but a large water change defiantly help in the late stage.

levels today:
ammonia-0
Nitrites-0.25 best I can tell
PH-8.0

I'll re-test tomorrow to confirm but I cant put fish in till this weekend so it should be lower or zero tomorrow and ill test nitrates

 

[Prowler66gt]

Nitrites are not a major concern in saltwater. As long as you are processing ammonia to near zero in 24hr and showing good nitrate then you will be good to add fish this weekend.

 

[brandon429]

I think we may be the only board on the internet relaying that info, that nitrite is neutral only in reef tank cycling

Neutral like: get rid of the kit and don't own it.

That shows Randy's impact wherever he's a resident. Rtr has the cutting edge info


So why ignore nitrite? Just to be avante-garde and force Lasses hand into a response? :) no

Its so you don't waste a second failing to plan for disease preps. Nitrite is neutral, but stocking order and timing sure isn't

We skip nitrite because of the chemical neutrality Randy highlighted in 2006 and it's so that we can then focus on the thing that kills so many fish, it has its own forum here.


Fish keeping has so much hassle I don't want any, it's coral only for me.

 

[r_mcwaters3]

Nitrites are not a major concern in saltwater. As long as you are processing ammonia to near zero in 24hr and showing good nitrate then you will be good to add fish this weekend.

So, after a few years of not keeping saltwater, it kind of used to be an issue, and new-ish literature says its not a big deal but old habits from tanks from 10 years ago always make me stress a bit lol


After re-reading Randy's Holmes article it makes sense that I can't really do any harm at low levels compared to what the ocean tries to do.

 

[r_mcwaters3]

I think we may be the only board on the internet relaying that info, that nitrite is neutral only in reef tank cycling

Neutral like: get rid of the kit and don't own it.

That shows Randy's impact wherever he's a resident. Rtr has the cutting edge info


So why ignore nitrite? Just to be avante-garde and force Lasses hand into a response? :) no

Its so you don't waste a second failing to plan for disease preps. Nitrite is neutral, but stocking order and timing sure isn't

We skip nitrite because of the chemical neutrality Randy highlighted in 2006 and it's so that we can then focus on the thing that kills so many fish, it has its own forum here.


Fish keeping has so much hassle I don't want any, it's coral only for me.

If I could do only coral, I might, but I really do love the look of saltwater fish. Plus my 7yo likes the fish more than the coral at his age

 

[r_mcwaters3]

Got home and tested:

Nitrite-0
Nitrate-10
Ammonia-0
Ph-8.0

Added 20 drops of ammonia and will see if the ammonia levels rise and settle in 24 hours if so I'm getting some fish Friday, whoo!!!! thanks for the help and support everyone. Ill post a quick update if levels rise and fall accordingly (which they should) and jump to the tank build forum after that.

 

[r_mcwaters3]

I come bearing good news, Ammonia was zero, Nitrites popped to about 0.5

I'm much more confident the tank is cycled and is ready for some clownfish

 

[hatteras hank]

I come bearing good news, Ammonia was zero, Nitrites popped to about 0.5

I'm much more confident the tank is cycled and is ready for some clownfish

Woohoo. Im hopefully only a little behind you. Started cycle on our new 15g tank after not having one for 7 years. On 4/11. Was hopeful for clownfish by Sunday but looks like next weekend at this point. Ammonia is finally coming down but nitrites still high and nitrates have been building up daily about 20ppm so it’s getting there. Haven’t done any water change. Hopefully will be ready for next weekend. Closest LFS is two hours away. Bummer. Congrats. Have fun. Can’t wait to see your tank progress.

 

[r_mcwaters3]

Woohoo. Im hopefully only a little behind you. Started cycle on our new 15g tank after not having one for 7 years. On 4/11. Was hopeful for clownfish by Sunday but looks like next weekend at this point. Ammonia is finally coming down but nitrites still high and nitrates have been building up daily about 20ppm so it’s getting there. Haven’t done any water change. Hopefully will be ready for next weekend. Closest LFS is two hours away. Bummer. Congrats. Have fun. Can’t wait to see your tank progress.

funny enough the better store around me is in Jax FL so about 2 hours for me to.

The water change helped for sure to expedite the nitrite issue and it took over a 50% change to get it to a reasonable level.

 

[hatteras hank]

funny enough the better store around me is in Jax FL so about 2 hours for me to.

The water change helped for sure to expedite the nitrite issue and it took over a 50% change to get it to a reasonable level.

Right on. I will see how things are looking tomorow and saturday. Might be close but maybe with a big water change will be ok by sunday. I imagine it will be fine to handle the small bio load a ton better starting with fish day one like previously. I know it’s processing well just not “done” by traditional standards. Have tested and recorded everyday since im excited and will likely never use the ammonia or nitrite kits again after cycle so get my moneys worth. Been cool to track it like a beginner again and enjoy the process. Never done fishless or dry rock and bottled bacteria start. Im old school.

 

[hatteras hank]

I got the IM as well. Couldn’t fit the 20g length in our space unfortunately so got the 15cube. It’s a smaller cuter version of the 34g cube i had 10 years ago. That was sumped though so this feels much smaller. Anyway. Have fun adding fishes and things. Will follow along.