amonia and ph

Question
hi has a slight disaster with my fish tank about 2 weeks ago added some new Fish from the pet shop and they all died within 24 hours had a massive amonie spike off the scale

is a 64 litre  interpret  fish box tank

i have cleaned the tank from all the old water washed  the glass with warm water cleaned the gravel ect... in boiling water and re set the tank up added the water conditioner and filter start


the issue in facing is that my nitrate and nitrite levels are on 0   amonia is 0.25  and ph high is quite high 8.8 with a normal ph of 7.6

( this is what im useing to test me water http://www.seapets.co.uk/products/aquarium-supplies/aquarium-treatments-fish-med )  

this is the filter start ( http://www.amazon.co.uk/dp/B002K659AI/ref=asc_df_B002K659AI8230039?smid=A3P5ROKL)    and the water conditioner is just the normal  one you can get from any pet shop same make thought.

any ideas as to why im facinb these issues

Answer
Nathan,
Since you cleaned the tank out completely, the filter is now going through the cycle process. It is always best to go through this 6 week cycle before you add any fish. I would also stop using the filter start since it doesn't work. The testing kit you are using is the best one. The fastest and safest way to get rid of the ammonia is through water changes. Since you have fish in the tank, you will want to test it every day and do a 30% water change if the ammonia and/or nitrites are above zero. Once the tank has cycled, it will be easier to keep the ammonia at zero.