Almost Cycled Tank?

[xamy_valox]

Hi,
 
I have had my tank up and running now for at least a year and a half. It recently had a strange moment where my levels became very obscure and practically all of my fish were wiped out save a handful.
 
At first my ammonia was very high, but no nitrates or nitrites. After adding some crushed coral to the filter it seemed to boost the tank into a cycle, where finally I was getting lower ammonia readings and levels of nitrate and nitrite. However now when I am testing I am back to having around 0.25 ammonia, 0 nitrate and 0 nitrite.
 
Is this possible after a sucesseful cycle? I was under the impression that there should be at least 5 nitrates as there always had been before this strange occurence. I was thinking though as I am using a Fluval U4 filter in a 125 litre, is it maybe that the tank is over filtered and under stocked?
 
Can anyone also explain why I may be having cloudy water? I put it down to a bacterial bloom but this does not appear in my testing?
 
Any help is appreciated - I realise this probably is an awful description!!
 
Thanks,
 
Amy

 

[benthyer]

I don't know a lot yet but am slowly learning. It is possible for a tank to enter into a mini cycle for a various number of reasons.
 
Have you changed or cleaned your media at all lately? Or made any changes to your normal routine?

 

[xamy_valox]

I think the tank went into a mini cycle because my PH levels dropped.
 
I am more worried about the fact that it seems to have finished the cycle, but yet I am getting no nitrate readings

 

[benthyer]

Maybe that means that it hasn't finished the cycle?
 
Did you ever get a reading of nitrites?
 
Hopefully someone who has more experience will come along soon and provide you with more help. I'm just trying to share what little knowledge I have

 

[xamy_valox]

Yes, at one stage I had readings of both nitrates and nitrites, indicting the cycle was under way.
 
Eventually everything calmed down which left me thinknig the cycle must be complete, but I have no nitrate readings all of a sudden!

 

[benthyer]

Have you recently completed a water change?
 
Does you tap water have Nitrates in it?
 
Have you got live plants in the tank?
 
It might just be the case that it hasn't built to a very high level, what test kit are you using out of interest?

 

[xamy_valox]

My last water change was a couple of days ago as I was reluctant to get rid of anything incase it needed to build up.
 
I am using rhe API Master Test Kit and I havent checked my tap water for nitrate levels, only PH.

 

[xamy_valox]

Here are my most recent readings.
 
I would say the Nitrate is slightly more orange than yellow, but I don't know if that is just wishful thinking..
 

 

[benthyer]

Doesn't look to bad to be fair.
 
Maybe just keep doing daily tests to make sure you don't get any spikes