My Tank Is Cycled!

[bogwood]

After 4 weeks, this morning my ammonia and nitrites read '0' (nitrates off the chart; PH constant at just over 7.0)... my tank is cycled?! I plan to get my first fish tmrw afternoon (Saturday).

I'm doing the large 60/80% water change (to remove the high nitr'a'tes) this afternoon. Once this is done, will it be ok to leave the tank - without adding more ammonia today to 'feed' the existing bacteria - until tmrw afternoon when I get fish? It will be around 24hrs between the large water change this afternoon and getting the fish in the tank tmrw...

... or should I put a tiny amount of ammonia in the tank tonight to keep the bacteria ticking over... I don't want to 'un-cycle' my tank by leaving it too long between adding the 'last' ammonia and getting the first fish!

 

[dwarfgourami]

24 hrs should be ok. Any more than that and you might want to put off the big water change if you can.

 

[rdd1952]

If your tank is cycled, you should be fine to add 2 to 4 ppm of ammonia again after you do the water change this evening. A cycle tank should easily be able to process 4 ppm of ammonia in 12 hours so tomorrow morning, you should be back to 0 on both ammonia and nitrite.

 

[timmystood]

Put a small amount of fish food in there - this should break down and release Ammonia