Ammonia dropped suddenly - cycle ending?

I've been taking daily readings from my tank as I've attempted to babysit it through it's cycle.

Today the ammonia has dropped considerably, but I haven't fed the fish.... so I'm not sure, would the drop in the ammonia be because my cycle is almost over, or because i've reduced the food and hence waste products? Obviously I'll keep monitoring it, but I'm just hoping this is the light at teh end of the tunnel.

As an example, here's the readings from the past few days, (I don't yet have a Nitrite test kit):

22/2 (normal feeding)
Ammonia: 3.7
pH: 8.0
Nitrate: 10mg/L

23/2 (normal feeding)
Ammonia: 3.7
pH: 7.5
Nitrate: 20mg/L (I dont have a Nitrite test kit yet)

24/2 (fed about 1/2 what I had been)
Ammonia: 2.4
pH: 7.5
Nitrate: 50mg/L

25/2 (not fed today)
Ammonia: 0.3
pH: 7.0
Nitrate: 110mg/L

All readings are taken in the afternoon, before doing a water change. The tank is now 20 days old.

It's really late, so thanks for the answers, and I'll get back to you with other readings when I wake up :coffee:

I have been doing the occasional KH test, and the pH is REALLY hard to gauge with the hagen colour samples, so it may not have changed as much as that looks. Next pay I'll probably invest in one of those elcetronic pH testers.

The water changes have been a pretty consistent 20-25% (about 9 to 10L)

and yes this is my home tank, not the work one.

One thing that seems positive to me is that all the fish are still active and 'seem' happy, and there is still a Glass Shrimp hanging about, and I hear they can be quite sensitive.

I'm trying to use as few chemicals as possible, because with such a small tank the balance is going to be hard enough to maintain as it is.

Also, I think the change in pH may be a reflection of the abscence of Ammonia, surely the fact that Ammonia is an alkaline and was in such high quanities in the tank would have been skewing the pH readings while it was spiking.

For the record, the new tank, before the Ammonia spike was giving consistent pH 7.5 readings, it only went to 8 while the Ammonia was there. Also, it's so hard to tell the difference betwen 7.0 & 7.5 with the Hagen test that it's more likely in the middle of the two

The Tapwater readings:
pH: 7.0
KH: 40 mg/L

Today's Tank Readings:
pH: 7.5
KH: 40mg/L
Ammonia: 0 to 0.1
Nitrate: 110+ (this is my new worry, another water change today!)

Ok.. ths is weird. I did a 20 % water change after that high Nitrate reading, yet today when I tested Nitrate, it was down around 5mg/L !! So I tested it again.. yep, it's all gone.

So can a 20% water chaneg have that big an effect? or could it be that my plants are chewing it up?

or.. are th tests just that inacurate? I still don't have a Nitrite test kit, so perhaps a final Nitrite spike was skewing readings? and now teh Nitrite bacteria have munched all that too?

I'm confused.

more research... :read:

at least the fish seem OK still.. I think it's going to be fine, just puzzled is all.