http://www.amazon.co.uk/gp/aw/d/B005...sr=8-1&pi=SL75
^^^^ cheap ph pen
I might be wrong here but i think you waters gonna be to warm? Idk
I had a pathogen problem at 20-21° c so i had to buy a water chiller and was told i could go down to 16°....idk maybe someone will explain .
I think its got to do with dissolvable oxygen in the water works best at a certain temp ?? Idk......im only going by what problem i had?
You may want to google your water temp.