Thanks for the response, I checked in the centre of the tank, middle of the water column with the API and centre of the tank however only a few inches down for the electronic reading (not waterproof for deeper testing). I ran the whole gamut of tests today and was heading back here to bump this due to some changes I have had I have questions about. I increased the CO2 after this original post.
Speaking to your flow suggestion, that may very well be a problem. I am running at SunSun 304B with a Hydor Koralia 750-850GPH as well as a small 20G HOB on the side as backup. I always wonder if there is enough flow. I sometimes wonder if the SunSun is not giving me enough GPH.
I found one dead and one lethargic and eventually dead panda cories at the bottom of the tank this afternoon. The 6 that are in there have gone through everything I have thrown at them in the year including a near fatal CO2 gassing one day. I have absolutely no idea what happened to them. One was missing chunks off of his dorsal fin however unremarkable otherwise. All of the other fish seemed perfectly fine as well.
Results from tests today:
pH 7.8 both chemical and electronic matched, done after about 5 hours of CO2 running today.
KH - 8
(total CO2 as per the chart 3.8ppm, low low low)
Ammonia - 0
Nitrie - 0
Nitrate - 40ppm
KH - 8
PO4 - ~5-10
I have dosed three days in a row now;
KNO3 - 3.47G
KH2PO4 - 529mg
(no trace ferts, going tomorrow to grab some)
The plants are pearling on their undersides beautifully, nice big bubbles by the end of the day which they werent doing last week. Clearly the CO2 is getting into the water and to some of the plants. I am slowly increasing CO2 flow to not distress the fish day by day, the bubble counter is showing almost a steady stream of air at this point there are way more bubbles than anyone could possibly count.