Is My Tank Fully Cycled?

[Boulder Fish]

I am on day 33 of a fishless cycle on a 20 gallon tank.

Nitrates went off the charts on day 14
Nitrites went off the charts on day 25

I continued recharging the ammonia each time it returned to 0.00 and waited five more days.
I did a 75% water change on day 30

My values on day 31 were:
Nitrate - 80 ppm
Nitrite - 0.5 ppm

Day 32:
Nitrate - 40 ppm
Nitrite - 0.0

What should I look for today?

 

[waterdrop]

Hi there boulder,

Need to know how much ammonia (ppm) you are putting in and how many hours its taking for each of ammonia and nitrite to get down to zero.

~~waterdrop~~

 

[Boulder Fish]

I am adding 3.5 ml of ammonia at each recharge, so 5 ppm is processing in under 14 hours (probably closer to 12, but I have not been able to test at exactly the right times.

So, today I recharged at 12:00 pm. It is now 10:00 pm and I get ammonia at 1.0 ppm, and nitrites at 0.5 ppm. Certainly when I get up at 6:00 am they will both be at 0 ppm

Ugh, I feel like I am being to vague.... does this make sense?

 

[locust267]

Are you able to recharge at 6pm instead so when you test at 6am its been exactly 12 hours?

Vicki

 

[Boulder Fish]

In theory, yes. But, somehow my 2 year old daughter has a way of throwing me off schedule. I am shooting for a 12 hour test interval today.

 

[locust267]

Lol, good luck with it. It will certainly help to test the efficiency of the filter and then other members who know a lot more than I do can comment on your results

 

[rdd1952]

It's odd that your nitrites took 25 days to go off the chart. Ammonia is converted to nitrite at the rate of 1=2.7. So 1 ppm of ammonia will yield 2.7 ppm of nitrite. That means that when 5 ppm of ammonia has been processed, your nitrite should be in the nieghborhood of 13 ppm and off the chart.

Another curious point is that your nitrate has dropped from 80 ppm to 40 ppm. I can understand that you cut it considerably when you did the water change, but it should not have dropped after that. There is nothing in a tank to break down nitrate. It is only removed via water changes.

If the tank is processing 5 ppm of ammonia to 0 ammonia and only a trace of nitrite in 12 hours or so, then it would appear that you are cycled, provided the nitrate is riding. If ammnia and nitrite are disappearing and the nitrate isn't rising, then it would indicate that something else is removing them and that they aren't being converted by bacteria.

 

[OldMan47]

Boulder, I'm guessing that you have lots of live plants in the tank. It's the only thing that I know of that will drive your nitrates down like that. As RDD said, nitrates will normally build between changes, not go down. That is true even in a fully cycled tank.

 

[rdd1952]

The live plants could also explain why it took so long for the nitrite to spike. Live plants will use ammonia in it's raw state so that it isn't processed by the bacteria thus meaning less nitrite and nitrate.

 

[Boulder Fish]

Thank you all for your interest and help.

Since I have been unable to post my reply, I'll go back to RDD's comments first.

NITRITES
I detected what I thought were just false nitrite readings on days 9 and 14 of the cycle that read 0.5 and 0.25 respectively.
Then on days 16-19 the nitrites hovered around 0.25 before becoming undetectable on days 20 & 21. I finally got 1.0 on day 22 and it continued to rise after that.

NITRATES
It is HIGHLY likely that the drop in nitrates the day after my waterchange was due to user error. I probably read the test in different light or something silly like that, because the nitrates are back off the charts. I only have two plants in my tank, and they are not what I would describe as robust. I did use Eco-Complete under black sand as a substrate, with the plan of adding plants later. Does that change anything?

NEW DATA
Two days ago, I tested at 11, 12.5, and 14.25 hours after adding the ammonia.

At 11 hrs: ammonia 1.0, and nitrites 1.0
At 12.5: ammonia 0.5, and nitrites 1.0
At 14.25: ammonia 0.0, and nitrites 0.5

(I reloaded the ammonia at this point, but wasn't able to check the tank for 23 hours,
at which time, ammonia and nitrites were at 0.0, again, I reloaded. That was last night)

Today, its a bit different.
At 12.5 hrs: ammonia 1.0, and nitrites 0.5
At 14 hrs: ammonia 0.5, and nitrites 0.25
At 16.25 hrs: ammonia 0.0, and nitrites 0.0

Is my "Mother of a Toddler" schedule slowing down the process? The great majority of the time I think I have been recharging as soon as the ammonia reached 0.0, but obviously not always. Perhaps the "Add Daily" method would have served me better (something to consider for next time).

At this time, though, how do things look for my tank?
Is 14-16 hours fast enough, or does it have to get lower?

 

[locust267]

I wouldn't say 2 plants would make a significant difference.

Ideally everything (ammonia and nitrite) should be processing in 10-12 hours before you are classed as cycled. You are almost there and certainly much closer than me!

I wouldn't say being a mum is slowing it down, however before you decide you are cycled make sure you can do another test 12 hours after reloading the ammonia to about 5pm and both ammonia and nitrite read 0 after these 12 hours.

Sorry for the waffle.

Vicki

 

[Boulder Fish]

Is there any benefit to doing another water change? Or just do a big change once I am at the 10-12 hour mark and am ready for fish? Is there any sense in continuing to test for Nitrates? Or again, just after the big water change?

 

[waterdrop]

Hi Boulder Fish,

At this point I think you may be down to some personal choice. You are very near the end of a standard fishless cycle and the ideal thing to do would be to bite the bullet and last out a bit longer by doing some water changes and seeing if you can see the filter get things down in 12 hours. The advantage of doing some large water changes is that you get to practice doing the gravel cleaning without any fish being in there, which is a little easier and its something you are ideally going to be doing each weekend anyway, so logistics and efficiency of method is helpful. At the same time you will be giving the bacteria just a little more time to try and get 5ppm of ammonia (& all the nitrite) down to zero in 12 hours. The gravelcleans/water changes will take out a lot of nitrite & nitrate which will be good at this stage also. Always recharge with conditioner & ammonia of course.

The alternative (the choice part) is to go ahead and do the final big water change, stop the ammonia and get an understocking of fish. If you were planning only a medium stocking then this should work out. The risk is that you will find the filter is still not quite fully cycled and you will have a somewhat worse situation (especially with a young one around!) of having to do water changes frequently as if you are in a fish-in cycle (ie. water changes until ammonia and nitrite are between zero and 0.25ppm, with repeats in an hour if necessary - you can see why the risk is significant.)

By standard vs. understocking I simply mean the usual 1 inch of fish body per one US gallon as standard stocking. By the way, I had the same thing where ammonia wasn't really dropping well until after about 21 days and only somewhat after that did nitrites begin to spike up to high levels. I later put that up to my tap water that had KH=0 (extremely soft, with no carbonate hardness, which bacteria like to have) and associated pH crashes down to pH=6, which causes the process to stall.

You sound like you are really very near the end, at which the last slow bit of waiting for the N-Bacs can be frustrating,
~~waterdrop~~

 

[Boulder Fish]

I will give it a bit longer and see if I can get closer to ideal conditions. While it would be nice to have some fish in there now, it will be so much nicer to keep them alive. Also, I've developed my stocking list and it turns out I have expensive taste.

Based on discussions on another thread, I plan to start small and add gradually. My current thinking (for my 20 gallon tank) is to start with 3 dwarf loaches, followed by 5 galaxy rasboras, adding 5 more as soon as I can afford them, and finishing off a few months later with one dwarf gourami.

As I was establishing that list, I considered less expensive alternatives, but ultimately agreed with the advice someone gave me about getting what I REALLY want to look at. After all, the fishless cycle should have its reward for me as well as the fish, right!?

So, though 3 dwarf loaches is definitely understocking this tank, I don't want to risk losing them.

 

[waterdrop]

Right when you finish a fishless cycle, the filter will have the capacity for a pretty full stocking, probably even more than a full stocking. Most people however won't fully stock because some of their species choices need a more mature tank. A mature tank doesn't mean one that's just cycled, it means that we don't really know what changes to the tank are needed but that we know from experience that waiting 2 months, or 6 months will somehow result in a tank that is usually much better for a delicate species - and of course opinions vary on the details.

If you have access to several of the hardier species that you want, its good to go ahead and get some in there. After that, your bacteria will die back down to support the initial stocking you've made. Then later, when you add more fish, you will need to do it in small numbers (2's and 3's) and let the bacteria catch up to each new added load. A tank less than a year old is not as fast at having its bacteria catch up to a fish addition as a tank that's older (ie. been cycled longer.)

~~waterdrop~~