I concur re the carbonate deficit. However, I would not be inclined to use baking soda. I would use a bag of crushed coral. This will work a bit slower but should not bump the pH which the baking soda will do. BTW- your 18.1 mg/l reading for GH means you have about 1 degree of KH. At least 3 dg would be better. However, if you cannot get any of the below, use the baking soda to try to get your cycle going again. This may be enough but you will have the same issue over time as the cycle naturally lowers the pH without enough carbonates and can stop entirely without them. The solution is a bag of crushed coral in the filter.
Thanks,
I've added the Bicarbonate of soda.
1. How many litres is your tank? What sort of decor is in it? Does it contain substrate? These reduce how much water a tank can hold.
Tanks is 54 litres, with 6 fake plants and one fake plastic object. Substrate is black polished style stone.
2. How many drops of the ammonium chloride did you add and how often did you add it? There are 3.79 litres/gallon so you should have added 4 drops/3.79 litres of actual water in the tank, not the stated volume of the tank.
I added 2.7 ml Ammonia Chloride on the first day and days 3 and 6 ( see below - I'm a fool!)
3. Did you allow for outgassing when you tested your tap pH? That is did you let the water sit out over night or did you bubble it for 10- 15 minuted before testing?
No will try this tonight.
4. Did you turn out the tank lights for a day and did you shake the Bottle of One and Only well before adding it?
Tank lights have been off the whole cycle. I added the whole bottle of One and Only and rinsed it out with the tank water.
Having read your update i've realised a massive error on my part.
The Dr Tim instructions state add Ammonia on day 3 and 6, as long as the Ammonia values are not above 5ppm.
I've now noticed that it also states not to add any more Ammonia after day 1 until the Ammonia drops below 2ppm. I completely missed this (although the two instructions contradict each other).
I added Ammonia on Days 1, 3 and 6 as per the instruction, which resulted in the reading of 3ppm each time. Obviously i now realise i shouldn't of added any more after day 1.
What do you suggest? Add more bacteria maybe along with a partial water change, or just wait having added the Bicarbonate.