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I have been fishless cycling for 8 weeks and everything moved along as expected except the Nitrites are staying at 5+ on my tests. After searching here seems like my next move should be:


Increase flow.

Add air pump.


I have 185 Gal fish tank, 175 Gal sump, two IBC media filled grow beds 12" deep.


Flow is currently changing out the fish tank once per hour. Only aireation is the returns to the sump from the grow beds, the sump to the fish tank and the pump return to the sump with excess flow running thru a down pipe with venturi holes in it.


Do I need more air?


Any other ideas, seems everything is working perfectly except bringin down the Nitrites...






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Hi Vhb, since you are fishless cycling, your next best move would be...well nothing. Just wait. You are in the "nitrite spike" phase of cycling it would seem. More air certainly hurts nothing, increased flow rate certainly hurts nothing...If you're antsy and need to tinker with that stuff, go right ahead, but probably none of that is necessary (from what you've described). Nitrite spikes while cycling with fish are the ones where the operator needs to be "proactive" about...salting, perhaps increasing flow, air, water changes etc...

IMO your just fine, just keep on doing what your doing and try to hold on to the patience that's kept with you up to this point

These buggers reproduce quite slowly (compared to many other bacteria).

I take it you've cut or quit NH4 dosing and all that?

Yes, I cut the dosing some 4 weeks ago. Thanks for the pep talk... I need it at this point. I was thinking 6 weeks max for cycling but I guess it is not a science.


I increased the flow just a bit and will hold there for now.



Cool temps make it a slower process, I think.  Just don't screw like I did by adding fish too soon.  Good luck.

Yep, it's just a slow process. That's the beauty of fishless cycling though. No need to take immediate action on anything, its completely hands off!

I agree with George, wait on your fish. I added fish to early also and have been losing some due to nitrite toxicity. I Wanted to wait but I had to take the fish when the hatchery truck was in town. Good luck and just hold tight.

Sounds like you have same problem I have my system is similar I am running 5+ nitrites and 5 nitrates but my ammonia is running 0 and my ph is 7.6 has always been 7.6  I am wanting to know if I need to bring up ammonia  and lower ph I am waiting on the nitrite spike to come down but not sure if I should change something. This has only been 12 days and the temp are low here in Illinois, the green house is helping but I am impatient also.   Hope  

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