The new GH boost method is maintaining the dGH, but the Ca:Mg is high. I am restarting MgSO4 20 seconds (3.3 ml) per day. The concentrations of ++Ca and ++Mg derive from their respective dissolution rates. As long as MgCO3 and CaCO3 media are present in the flow path, both solutions will be constant in the effluent (determined by pH and flow rate). As a practical matter, the cation ratio cannot be readily adjusted through this method. Finding the correct supplementary dose of MgSO4 required to redress the deficiency will be a much easier experiment.
The KH and K are maintaining spot on, and have been for some time. The K2CO3/Alkaline Buffer mix and dosing rate are just right.
I have seen no effects so far of raising the pH. The one effect I would expect first might be appearance of algae, especially with the added light. Although the new lights have increased the oxygen tension to its normal elevated level, they are throttled to 75%. I will be interested to see the utilization rate of CO2 after a couple of months of this. The streaming water change regimen is holding the system in strict oligotrophy and the redox is exceptionally high. DOM, orthophosphate, and DIN are running very low. The plants are growing and have great color and there is no sign of algae as yet.
Today I am feeding fresh frozen and sinking green.
The Nymphaea has not bloomed in nearly a year. Today we have a flower.
Both the pads and the big, old swordplant leaves throw considerable shade. I trim the oldest and the most tatty. With the lillypad, I remove five or six at a time. This plant is prolific. It is constantly putting up new leaves, sometimes two or three at a time, and they grow FAST. To remain healthy, the plant needs a minimum of two mature floating leaves in order to conduct its vital gas balance. When I trim, I leave three or four. They are usually full grown and quite large, so there is still shade. Two things to bear in mind: 1) the plants being shaded, Java fern and crypts, are shade tolerant, and 2) the attenuation of the light discourages algae. When I do a major pruning, the surface really opens up. The tank is brighter then, and it has a different 'look', but shade sets in quickly as the large plants answer back. This is a kind of natural thing, and I also like the 'look' of the tank with life happening at the surface. The sag and hygro overspread and the sag and swords put out lots of flower runners. This is when we often see cherry barb fry.
Redox is unusually high. If I were running an ozonizer I would regard this as dangerous. The O2 in this system results from ordinary circulation and photosynthesis in the plants. The running average oxygen tension is 6.9 ppm, with a brief daily peak of 9.6 ppm (saturation) at 19:00. The ORP should gradually rise absent introduction of reducing organics, i.e. pollution sufficient to drive redox down; and if the stimulus conditions persist, a consistently high ORP should not be at all surprising. The principle stimulus conditions are rapid removal of autochthonous DOM (fresh turnover) and illumination that promotes robust carbon fixation with the resultant O2 generation. This ecosystem's oxidative potential is strictly "as results" from natural conditions; there doesn't appear to be much I could do about it. There are no strong oxidizers (peroxide, permanganate, ozone) present. Now on a more speculative note, I believe the ecosystem is responding on a profound level to the water change regime. The effects are multiple, gradual, subtle, and pervasive.
The GH, KH, micros, and potassium are stable at the present dosing and water change rates. While there is still some tweaking to be done, I am confident that the balance has been struck. I am very much okay with the pH at 6.8. The O2 cycle is ideal with the lighting where it is, there is no nuisance algae; plants, fish, and snails are happy. Interestingly, PO4 and NO3 are variable on a daily basis with no obvious correlation as yet to the feeding schedule.