Still not getting a consistent baseline non-zero value for Fe. I am bumping up Flourish Comprehensive to 160 seconds, 26.7 ml, daily.
The hardness values are back in the desired range. Today I am installing the 250 gram charge of Reef Reactor in the 130 gph loop. Also, time again to change out the intakes. I will continue withholding K2CO3 and MgSO4.
Resume K2CO3 dosing. Bump daily dose Flourish Comp up to 240 seconds, 40 ml. The trace below is the current oxygenation profile. Midday 27 May I changed the aeration threshold from 6 ppm to 5.7 ppm. Note that the daily saturation peaks drop off slightly and the air pump works just a little longer in the early mornings. This signals increasing shadiness, meaning it's time to trim and clear the overgrowth.
I completely stopped CO2 flow to the left end diffusor and still get increasingly declining pH-L. I suspect the reliability of the pH-L probe, so I am not incorporating it in the running average report. I will re-calibrate the probes, but I'm thinking one or the other may need to be replaced. I am installing a third, independent meter (Milwaukee MC110) and will be experimenting with probe placement to try to identify the problem.
The reconstitution/water-change balance is pretty close to equilibrium, but it appears from the GH trend that perhaps 250 g of Reef Reactor is just a little short of requirements. Today I am adding another 100 g to the filter bag to see if I can get closer. I doubt it is possible to get continuous equilibrium on a specific dGH value, but I consider it a success if I can achieve a reasonably stable foundation GH, with only small ad hoc adjustments using CaCl2/MgSO4 solution. The Reef Reactor is providing some background potassium and buffer support but is not sufficient. The current total daily dose of 40.5 ml K2CO3 (100g/liter solution) is maintaining the target values for +K and dKH.
The dose rate for Flourish Comp is an ongoing experiment. After Friday's high, I reduced it again. The current daily dose of 20 ml results in post-dose Fe values circa 0.1 ppm and zero pre-dose every morning. According to SeaChem this may be about right, but I suspect it's a little too lean. It is under target baseline, so I have bumped the dose to 28 ml. As a point of interest, this dose rate is over twice SeaChem's max recommendation for a densely planted tank, but it must be accounted that the streaming water change regimen dilutes the dose over the course of the day. The water changes and dose rates regulate the concentrations cooperatively.
At the current water change rate, autochthonous DOM, NO3, and PO4 persist well within oligotrophy. High redox is super-stable. I attribute this to the streaming water change regimen. While chemical filtration certainly impacts the DOM in particular, the key to maintaining this favorable condition is in the incessant changing of the water. A downside is the effect on the micronutrient economy, but in the cost:benefit calculation overall that's hardly a deal-breaker.
One week ago today, 9 June, at 13:15, the Apex Classic Aquacontroller base unit stopped functioning. It was necessary to replace it with a new "2016 Apex". All programming was irretrievably lost, so once the new unit arrived, the entire system had to be re-entered. The datalog begins a new history as of now. In the downtime the dosing, CO2 injection, and streaming water change regimen were on hiatus. Power for pumps and lights was routed around the Apex interface. I did one 10% water change, fed sparingly, did one day's blackout, and ran the UVC sterilizer continuously. The temperature bottomed at 74 degrees. The pH, monitored by the newly installed Milwaukee Instruments pH monitor, stabilized at 7.4. Fish and plants doing just fine. As of 18:00 yesterday, all functions are back on-line and schedules are resuming their normal routines.