Coming To The End Of My Fishless Cycle.....next Steps?

[MikeO]

Today is day 43 of my fishless. Just taken 12hr readings for everything and they are as follows:


Ammonia = 0
Nitrite = 0.1
Nitrate = 110 (As expected)
pH = 7.5
KH = 2.79
GH = 7.82

So it seems it is virtually at the end of the cycle.

Obviosuly I need to do a 100% (or thereabouts) water change - if I do this now, before adding stock, and continue to dose the tank to keep the bac alive, then will the nitrate carry on increasing again, or should this not happen now that the n-bac is established? Or is there a better time to do the water change - i.e a set number of days before I stock the tank?
I am keeping mbuna, so I am concerned a little about the pH and KH. I already have 40kg of limestone in the tank and caribsea eco-complete cichlid substrate, which is pH buffering, so am suprised at the outcome of these tests. Should I look to add some crushed coral to the filter too, or is there anything else I can look to do which will improve the conditions a little?

Thanks as ever!

 

[scotty]

i believe you have to have both nitrite and ammonia at zero,then you would have a qualifying week where both are at zero,when doing your twelve hourly tests

 

[waterdrop]

Hi Mike,

You are falling into the trap of allowing your water parameter readings taken at -any- time during fishless cycling to be used to "think about" the water parameters you want for your fish later, after fishless cycling. Its better to never do that. Although we all think we can mentally do this, it often turns out that the fishless cycling process itself is throwing things farther off than we realize.

The high nitrate(NO3) levels seen near the end of fishless cycling have a significant nitric acid component that is quite powerful in driving pH down. It is my feeling (unsupported) also that some aspects of the chemistry in these late stages and with lots of nitrate is that it seems to hang rather tightly with the substrate, so sometimes it takes several good gravel-clean water changes around the time of the big switchover from fishless to with-fish to completely change over the water chemistry.

Scotty is right, you are in the final "sticking problem" stage of fishless cycling. It takes a filter 6 months to one year to grow the two bacterial colonies and to become truly "mature." Choosing a point in time to call the filter "cycled" is really a matter of judgement and guessing. At TFF we've chosen our compromise to consist of a "qualifying week" test revolving around the 12-hour test. But there are members that point out that double-zero results at 8 or 6 hours after adding ammonia are even better - I only point this out to show that its really kind of a continuum.

So the way our test works is that once you have a day when you put in ammonia at a 5ppm concentration and note the time. Then, if 12 hours later you test (with your liquid tests) and find that both ammonia and nitrite(NO2) have dropped to a true zero ppm, then you are ready to start your "qualifying week." During this week (which might be technically a little less than a week if it takes you to a convenient weekend for the big first stocking!) you just keep testing and adding ammonia and confirming that you keep getting true double-zeros day after day. We've found this test to be very effective at forcing any surprise mini-cycles that might beset the filter and to be pretty much as good as waiting for the cycling to get down to 8 or 6-hour double-zeros.

If you keep seeing a "trace" of nitrite (as in your last test) for a week or so, don't despair: this is the "sticking problem" that we see a -lot- and it does indeed go away. The cycle is significantly stronger after you get past that and qualify the filter. Also, don't be afraid to do a 90% gravel-clean-water-change and recharge with ammonia as a way to help get past the sticking problem.

When you do the big water change, most people time this to be within 24 hours or so of the initial stocking (the logistics of this can be difficult!) If you want to do another ammonia charge to drag things out to 48 hours then I'd maybe at most do one of these, although technically I suppose you could drag this on further. But the problem is that 5ppm of ammonia going in is a lot and you really will be producing nitrate(NO3) again quickly, and you just want the most pristine water possible for the move-in of your fish, since moving is stressful on them anyway.

~~waterdrop~~

 

[MikeO]

Thanks guys.

I think I may do a water change tomorrow - I did a 90% change last week and at that point the nitrite at 12 hrs was 0.3. Whether this helped get to where it is now I dont know, but I think I would like to get the nitrate down if this is in fact pulling the pH down - I didnt realise this happened, so dont want to add coral if its actually lower than what it will be once its fully up and running.

Would the high level of nitrate also pull down the KH figure?

A little while longer to hold off before placing the order at the LFS then

 

[waterdrop]

No, the nitrate would not pull KH down. It only pulls the pH down. WD

 

[MikeO]

I just did a 6 hour test just to see out of interest where it is at.

Ammonia = 0
Nitirite - 1.6

Will see what is happening at 12 hours again tomorrow to decide on if I do a water change.