Firstly, I would like to thank everyone (especially Byron) for your thoughts. I really appreciate hearing the ideas and experiences of others.
Now, Byron you state that keeping fish is all about science. I agree to a point, it is most certainly NOT an exact science therefore allowing for many variables.
I am satified with the research I have undertaken to get the right balance for my tank. Having this tank only for the past 6 months has seen mistakes made and lessons learnt the hard way. This is all part of having fish as far as I am concerned. I have had no fatalities throughout this settling in period so, I must be doing most things right.
The PH variances have not been recent. That was more in the very beginning when the Nitrite/Nitrate/Ammonia factors were still establishing. For the past 3 months (I have been keeping detailed diary notes including everything from water changes, chemicals added and why, when new fish have been added etc etc) my PH has been stable at 7.0 - 7.2 which, has not caused any obvious issues.
I have had issues with the Nitrite and Nitrate however, that is all under control now. As for the high Phosphate reading, it is my understanding from further research that this is not really a huge issue in fresh water tanks. It may contribute to high reproduction of algae however, this has not been identified in my tank.
Thank you once again to all who have helped me to get a better understanding, I really appreciate you each taking the time to respond to my questions and concerns.
Just for interest sake Byron, here are the details of my tank:
5ft x 2ft x 2ft
Substrrate - River sand
x2 large driftwood with Anubias
x3 Silver Dollars (palm size)
x5 Clown Loaches (3 - 7cm, 2 - 10cm)
x4 Corydoras (fully grown)
x1 GNF (approx 7cm)
x1 Royal Whiptail (mature male)
x1 Long Finned Bristlenose (10cm)
x4 Kuhli Loaches (5cm)
x2 Angels (medium size)
x10 Zebra Danios (juveniles)
x10 Black Tetras (mid size)
x2Large bunch of Alodea Java Fern
Filter is Eheim Classic 600
Water changes, 25% weekly. 50% once per month
Filter Clean, once per month