This is what I ended up doing. Started out low tech but very heavily planted. Came across a chart showing a particular plant growth rate relative to CO2, showed a big increase up to around 15ppm CO2 after which growth levelled out somewhat.
So, now I inject CO2 to an estimated 15ppm, made up 2DKH solution for drop checker, so still lime green/yellowish at lights on. I use Darrel's DWI and dose LushMax heavily. If I don't, the floating Ceratopteris nicks all the ferts and my Limnobium tells me so. Change 30% per week. DIY HFM over a weir. Lighting PAR is unknown as it's a DIY programmable LED system. I only keep easy plants but the Jungle val leaves reach over 4 feet!