Cycling Gone Backwards!

[jonnyf84]

hi,

i'm in a bit of a unique situation. I set up my tank over 2 months ago, but because i've been waiting for co2 and other equitment i have had no fish in it yet, because of this i have been dosing ammonia to keep the filter running, it has been completely cycled for over a month now and i have had no problems - it has been converting about 20-25ppm of ammonia every day!!

Now, i got all my plants a few days ago (it is a aquascaping tank), i put them in and started to have the light on for 6 hours a day (light previously un-used). Now the ammonia consumption has slowed down to 5ppm per day and nitrites are really high (previously 0 of coarse), there is still a reading of nitrates but it seems like the cycle has gone backwards - the tank is no longer cycled.

Why has this happened and what do i do?

many thanks,
jonny

 

[OldMan47]

I hope I don't understand what you have been doing. If you have been dosing enough to get the ammonia up to 25 ppm and then doing the same the next day, you have been raising the wrong bacteria. If you have been dosing for 5 ppm 5 times a day, you may still be OK. The bacteria that we want in our tanks to process ammonia will lose the competition with other bacteria if the ammonia concentration gets much above 8 ppm. When you put plants into the tank, they will use the ammonia as plant food as much as they can. That will leave you with a lower concentration of ammonia in the tank which will not be high enough for the bacteria you have been raising but the others are not present in great enough numbers to step in and take over processing the remaining ammonia. I would dose only to 5 ppm once a day and let the plants take their share of the total. If your chemistry is back to zero ammonia and nitrites in the next 12 hours you can count yourself lucky. If you have residual ammonia, just bring the levels back to 5 ppm once a day and complete the cycle using the right bacteria, there are probably some of them present. By not going over 5 ppm, you will be culturing the right bacteria this time.

 

[jonnyf84]

well crap!!! how could i not know this. I have generally dosed the tank twice a day at 10ppm, since getting the plants i have knocked it down to 5ppm twice a day and since i have been doing that is when the problem started.

So you think i should just dose 5ppm once a day and then the cycle will complete? How long do you think it will take as it surely wont be like starting all over again?

should i do water changes?

 

[OldMan47]

I have never been in your position so it would be hard for me to guess. At the least, you will have some of the ammonia processing bacteria present that we do want. That should give you a jump start on getting the bacteria established at a good level. I would expect it to take less than 2 weeks with that start already going.

 

[jonnyf84]

I have never been in your position so it would be hard for me to guess. At the least, you will have some of the ammonia processing bacteria present that we do want. That should give you a jump start on getting the bacteria established at a good level. I would expect it to take less than 2 weeks with that start already going.

thanks old man, should i bother to add a established filter from another tank? I only have established Fluval 2+'s, i'm not sure this will help too much as its the fluval 105 that needs to be established before i can add fish.

 

[OldMan47]

I would wait a day or two and see what you have. That 105 may come back pretty quickly if it has a decent amount of the right ammonia processing bacteria in it. Otherwise, if you can spare a sponge out of the 2+, it would help get the 105 going with the right bacteria. Even doing a clone like that would mean a week of trial and you may recover almost that fast because the 105 probably has some of the right bacteria in it.

 

[jonnyf84]

thanks for your help old man. I can't believe i didnt know this.

 

[OldMan47]

I spend some time in the scientific section where the discussion often goes beyond the advice we give new people. I don't post much there, mainly just read a lot. Now and then it does give me some insight.