Pughie1993 Pughie1993
  • Just popping in
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  • Joined: 12/1 20:14
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  • Posted on: 12/1 20:26
Tank cycling again? Please help! #1
Hello everyone!

I’m in a pickle at the moment and I could really do with your help and advise! I’ve been keeping fish for 2 years now and I have just changed my tank. I’ve now got a new 80 litre tank which I cycled for 5-6 weeks back in September/October time. I can’t remember the readings now but everything seemed to be fine. Anyway I swapped the tank over and it was all fine until a few weeks ago when I had an ammonia spike of 0.5ppm. I have been checking the tank readings daily and doing 25% water changes to try and reduce the ammonia and nitrate . The current readings are:-

Ammonia 0.5ppm
Nitrate 40ppm
Nitrite 0ppm

I’m also adding bacteria into the tank with every water change. As I was planning the tank swap I forgot to keep the filter media wet 😪 I think this is what had caused the problem. I presume the tank is cycling again. 😣😭 I feel terrible because I know it’s not doing my fish any good and I’m just st a loss at what to do. A few more bits of info are-

Fish:- 2 bronze Cory cats
X5 endlers
Fighting fish
Planted tank
Aqua flow 300
Temp is 26C
Also has a air stone
Using bio safe water conditioner

Any help will be much appreciated.


fcmf fcmf
  • Coldwater Adviser
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  • Joined: 17/10/2014 11:20
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  • Posts: 521
  • Posted on: 13/1 15:07
Re: Tank cycling again? Please help! #2
Yes, it seems that what has happened is that, between you cycled the tank (or, more accurately and best to think of it as, cycling the filter) and then actually put fish in the tank, the beneficial bacteria built up during the cycling process went dormant and then died, so you're now doing a fish-in cycle. [This article helps explain the fishless cycling process well: https://www.fishkeeping.co.uk/articles ... hless-cycling-article.htm.]

What you ought to have done between finishing the fishless cycling process and introducing the fish was to continue dosing with ammonia as per instruction no.6, and then done a large water change to reduce nitrates just before moving the fish into it. Alternatively, the newer tank would actually have been instantly cycled by moving all of the filter media out of the former tank's filter and into the newer tank's filter at the same time as moving the fish.

The best way to address the problem you now have and reduce the ammonia and nitrates level (and keep nitrite at zero), now that the fish are in it, is here: https://www.fishkeeping.co.uk/articles ... ammonia-nitrite-spike.htm

On a separate note, keep an eye on the endlers and the betta(s) (fighting fish) - often bettas try to fight with fish which have flowing tails like their own. If you've had them all for 2 years without issue, then hopefully they'll be fine, but, if not, keep an eye on them and be prepared for a back-up plan such as a new/separate tank for the betta(s) if problems arise.