Help, contaminate from manual co2 in tank!!!

I have a 260L Jewul Vision tank, fresh water.

I use a manual co2 which has yeast, sugar and water in. A much cheaper
alternative to the other co2 kits. Problem is, we have just had
kittens which knocked it over which, due to the volume of stuff has
forced some through to the tank (probably a couple of days). I noticed
when i got home 14:00 (04/02/05 tonight), that the tank was really
really cloudy with several fish dead. I did a water parameter check
and it turns out that i now have levels of ammonia and nitrites which
i never have as i do regular water changes and i check the water every
week. I've done a 30% water change and put in some toxivec which is a
pollutant remover (I've never used this before, and was recommended by
my local fish shop).

My gut is telling me to do another change tomorrow morning (probably
about 100%) change as alcohol, yeast and what ever else has made it's
way into the tank. The tank is still really cloudy.

I've now found another dead fish, and i think all my shrimps are dead.

Any advice would be appreciated.

Thanks

Russ