Am I bypassing my nitrogen cycle? 8g biocube

[Jeffs]

Hi,
I have set up my biocube 3 weeks ago and because I have not done much reading, have decided to add fish only two days after setting up. My LFS gave me a bag (approx 3 cups) of "dirty water" which is basically water squeezed from a used sponge with brownish dirt and was told this would help speed up the nitrogen cycle. I have already purchased API test kits and realized that I have no major ammonia spike. I have been testing the water everyday since I'm trying to avoid fish deaths. First few weeks I'm getting ammonia of about .25-.5 and I have been doing twice weekly 50% water changes. Lately, I am getting 0 ammonia and 0 nitrite and 10-20ppm nitrate. I asked my LFS and he told me its good news means that my tank is cycled.I am keeping Weitzmani tetras, scarlet badis, boraras merah, an amano and crystal reds and have lost none so far and they seem to be swimming and eating fine. But where is my ammonia? Question is, do you folks really think my tank is cycled or just waiting for future problems? I was told that the plants may have well soaked up ammonia, is that true?? Sorry for the questions newbie here.

pic of tank:

http://www.aquariumadvice.com/forums/attachment.php?attachmentid=16066&stc=1&thumb=1&d=1226198336

 

[SpeedEuphoria]

You did have an ammonia spike as you said you were getting readings of .25-.5. Since you had a source of bacteria from the LFS I think your good to go.

 

[gzeiger]

An established tank should always have no detectable ammonia or nitrite unless you disturb something. The presence of nitrate indicates that your cycle is complete - the bacteria in your tank are eating all available ammonia produced from fish waste and converting it into safe nitrate.

 

[OldMan]

I would watch the nitrates for a bit and make sure they are going up between water changes. If they are, you may well have finished off a cycle for the amount of bioload that you have right now.

 

[Jeffs]

I would watch the nitrates for a bit and make sure they are going up between water changes. If they are, you may well have finished off a cycle for the amount of bioload that you have right now.

Nitrate levels are still the same (20ppm) regardless of water change. Is something amiss?

 

[OldMan]

Check your tap water's nitrates. I am guessing that you have continued your twice weekly 50% water changes so that is keeping the ammonia and nitrites near zero. I would guess you will find the tap water nitrates around 20 ppm and your cycle has not really started yet from what else you have said and have not said.