Post Cycling - The New Normal?

I'm in the 6th week of cycling a new 32g tank (with fish & bio-enhancers), and I think I'm near the end of the cycling process.

As expected, it's been a bit of a bump ride with a lot of water changes in the 4th-5th week to keep PH near 7.0, and drive down nitrites when they got a bit too high. Suddenly the last week everything is much more stable with no water changes needed.

PH = 7.0
Ammonia = 0.0 (but slightly yellow-green)
Nitrites = 0.0 (with a one test blip of slightly pink water - otherwise clear water)
Nitrates = 5 (maybe slightly higher, like 6)

I added 5 small fish about 10 days ago and I think there was a tiny blip in the ammonia & nitrites in terms of slightly darker color for one test.
My entire bio-load is 18 fish, 15 of which are about 1" and 3 of which are about 2". No live plants.

I guess what I'm wondering (and cant recall from my past fish keeping experience) is what sort of change should I be seeing in the nitrates to indicate 'yes, everything is working like a cycled tank'? It's been around a week with nitrates maybe moving slightly from 5 to 6 (very slightly darker pink color in the test results).

Does that sound right? I was expecting it might be moving upward faster, but I think the last time I kept a tank I had a larger bio-load (larger fish).

Here's a picture of my 32g tank to gauge bio-load.

With no live plants you should expect to see some nitrate. 3 ppm was chosen as the amount of ammonia to add during fishless cycling as this is more than a fully stocked tank makes in 24 hours. But just how much ammonia your less than fully stocked fish are making is something we can't know.
Nitrate testers are the least accurate of the ones we use. When my son worked for a water testing company he was highly amused by our tester. It takes very expensive lab equipment to get an accurate reading.

I wouldn't worry about the amount of nitrate increase, just the fact that it does increase is good enough. It's when it goes up a lot during a week that you need to worry as that means you have too many fish or are feeding too much or are not cleaning the tank and filter enough (muck in/on the substrate and goo in the filter decompose to make ammonia which is turned into nitrate)

essjay said:

With no live plants you should expect to see some nitrate. 3 ppm was chosen as the amount of ammonia to add during fishless cycling as this is more than a fully stocked tank makes in 24 hours. But just how much ammonia your less than fully stocked fish are making is something we can't know.
Nitrate testers are the least accurate of the ones we use. When my son worked for a water testing company he was highly amused by our tester. It takes very expensive lab equipment to get an accurate reading.

I wouldn't worry about the amount of nitrate increase, just the fact that it does increase is good enough. It's when it goes up a lot during a week that you need to worry as that means you have too many fish or are feeding too much or are not cleaning the tank and filter enough (muck in/on the substrate and goo in the filter decompose to make ammonia which is turned into nitrate)

Click to expand...

Thanks essjay. The tank does have a rather larger dual filtering system, with two sets of large sponge filters, both currently containing Fluval Biomax packs. So it could be that the fish just aren't generating that much ammonia, and it's been that way most of the cycle so far. I had one point a couple of weeks ago where NH3 registered slightly and TAN was around 0.4, along with a nitrite spike to 0.8. Nitrates jumped up as well and hit somewhere between 20-30. A few 20% water changes in the coming days seemed to have remedied those dangerous levels and has hit a point of greater stability.

I'm hoping that I've judged the fish bio-load correctly, anticipating that as some of the fish grow, particularly the pleco, there will still be room for the 'good bacteria' to grow in response.