Shit...

Water went cloudy in the space of 15 mins.

Did nothing but add a rock and feed them.

Tested immediately - HIGH levels of amonnia

Doing a 50% water change as we speak, but how can I get this situation under control in the medium terms (I have to work all day tomorrow so cant be doing constant water changes all day!)

You could use primer or the de-ammonifiying stuff that changes ammonia is less hurtfull ammonia.
WC will be necsesary, but doing a 50 % a day will be enough,IMO.
You can allways change some water before you leave and do the same when you go home.
How big is your tank?
When my tank was suffering from nts as a nubee i resolved to 80% WC with primerand add liquid bacteria, but that can stress the fish even more.
Better find out what caused the spike!

These spikes do happen on occasion and often don't last very long. Exactly how high was the ammonia? I would have thought a 50% water change would keep the situation under control. Don't check your water straight after the water change as you could possibly get a false reading, trust that a water change has eased the situation and do a water test tomorrow. As to why this happens, have absolutely no idea

OFL wrote:



Ammonia was off the chart on the test kit I have, it really isnt very accurate.

Yeah dont know what happened - pulled everything out of the tank so I could check all fish are accounted for...no one missing. Did a 50% water change but hasnt seemed to change the situation much. Have addded plenty of prime which states that it de-toxifies the ammonia, will hope that it works as it is 1am and i need to sleep.

You rarely get instant results with fish tanks, things settle down over a few hours or even days. So keep doing daily 50% water changes until ammonia is zero. Test before a water change