200 GALLON JUNGLE

Exactly so.

Exposure to ultraviolet will denature organics. The ligand bonds in gluconates, EDTA, and other chelation agents are intentionally weak so that the nutrient component will be easily released under ordinary natural conditions, such as normal daytime lights. UV will cause rapid photolysis of these molecules, thus interfering with the bio-availability of the nutrient.

The effective kill for protozoan parasites with a 40 watt UV'C' sterilizer requires minimizing the flow rate to under 300 GPH, while under 900 GPH is adequate for bacteria, planktonic algae, and algae spores. In my system, the sterilizer is plumbed in a parallel loop after the filters with its own flow meter so that it benefits from delivery of polished water influent (25 microns; irradiation density increases with water clarity) but can be throttled by adjusting the aperture of any valve in the loop without slowing system throughput. System minimum flow rate is 550 GPH, but I can "dial in" sterilizer/chiller flow-rate to under 300 GPH independently.

The sterilizer operates on a 50% duty cycle in the interest of preserving supplements intact. Also, bulb life is doubled. This is a necessary compromise, but in a short time the entire water column will be exposed.

Today's numbers

pH: 6.75
TDS: 280 ppm
NO3: 13 - 18 ppm
PO4: 2.5 ppm
Fe: 0.19 ppm
K: 30 ppm
dKH: 6.0
dGH: 3.9
Ca: 17.6 ppm
Mg: 4.9 ppm
Ca/Mg: 3.6

Testing is central to my method. For the record, I should here present the testing protocol which governs the water chemistry under the water change regimen presently being used.

I have done the calculations* for the water change stats for this regimen. Of course, these calculations assume complete water column remix at the influent of the circulation pump. Also, the numbers are based on the tank water volume = 200 US gallons (757 L) exactly. So these results should be understood to lie on error bars. But for practical purposes they are valid approximations.

The daily net new water retention as a percent of tank volume is 6%. This effectuates a weekly water change of 36% and a monthly (30 day) water change of 85%. The purpose of the water change regimen is to export autochthonous DOM. The essential question is whether this rate is sufficient to control DOM concentration at the rate at which this waste loading evolves. The scheduling of an occasional "big gulp" water change, such as 10% or 12% of tank volume in one go, might assure good karma (which is to say it will certainly do no harm and could even prove necessary). When the mechanical filters are changed and the bio-media are rinsed the canisters are partially drained. I will take note of this water change.

The normal system flow rate is 570 GPH (2158 LPH). When this drops to 550 GPH, the mechanical filters are changed. One full circulation cycle with mechanical and biological filtration in line processes 99.9% of the tank in about 2.5 hours. This throughput is just under 10 cycles daily.

The sterilizer loop running at 300 GPH (1135 LPH) processes 99.9% of the tank in about 4.5 hours. The sterilizer is ON for 12 hours daily, so the throughput exposed to radiation is about 2.5 cycles daily. The flow rate is throttled in this loop to increase dwell time in the sterilizer, 300 GPH being the generally recommended velocity limit in a 40 watt sterilizer to achieve a significant kill in one pass of protozoan parasites. But there is a defined minimum to the total throughput which is set by the reproductive rate of the target organism. I expect to be okay here, but I have no meaningful dataset.

*hamzasreef.com > Effective Water Change Calculator
hamzasreef.com > Pump Turnover Calculator

About substrate:

When the largest part of the substrate used in this tank was first put in, winter of 2008-09, my awareness level with respect to commercially available organically enriched planting media was not high, and it was not so widely used then as now. Nor was I then a diligent student of the Walstad method of soils. The use of substrate heating coils was thought to improve nutrient distribution in the substrate. I considered that very briefly.

This is washed river clastics on the Wentworth Grain Size Classification scale between 0.5 mm coarse sand and 4 mm granule, which is mostly quartz and typically sold as aquarium gravel. I had a large quantity of old gravel from previous tanks. To this I mixed generous amounts of CaribSea Eco-Complete, SeaChem Flourite, and granulated laterite. So the substrate was essentially inert with some enhanced porosity and cation exchange capacity. Over time mulm, or POM (particulate organic matter), accumulates and works its way into the gravel, enhancing its organic content. At the present maturity, this substrate is no longer inert.

For a while I made a practice of regularly emplacing root tabs, solid fertilizer tablets, around the swordplants. That has stopped. All allochthonous supplementation is via auto-dosed solutions. The ions diffuse by concentration gradient alone. The rhizosphere in this aquarium seems to be handling nutrient transport just fine.

Karen Randall's overview and advice about substrate reflect my own. Another excellent resource for the aquatic gardener.

Randall, Karen A. Sunken Gardens: A Step-by-Step Guide to Planting Freshwater Aquariums; Timber Press 2016

Today's numbers

pH: 6.75
ORP: 536 mV
TDS: 310 ppm
NO3: 20 ppm
PO4: 1.46 ppm
K: 30 ppm
Fe: 0.11 ppm
dKH: 6.5 ppm
CO2: 31.4 ppm
dGH: 4.1 ppm
Ca: 17.6 ppm
Mg: 7.3 ppm
Ca/Mg: 2.4

The source of buffer in this system is exclusively carbonate, CO3 -2. At pH = 6.75 all carbonate radical converts to bicarbonate (HCO3 -1), and the dissolved inorganic carbon, DIC, is HCO3 : CO2 = 60 : 40 (approx).

The alkalinity in this system is higher than is perhaps typical in planted aquaria. On a scale of what is possible in natural waters, this carbonate hardness is moderate and fully within healthy limits. I will concede that in natural soft waters, such as rainforest primary streams where the dGH is 4 to 5 at most, the KH is usually commensurate. However, judging from conditions generally, and vitality of the plants especially, the bicarbonate concentration does not appear to exceed the adaptability of the plants or fish I am working with. The KH could be brought to under 6 degrees, but then the pH would have to be lowered to 6.70 to maintain circa 30 ppm CO2. I prefer to control the CO2 concentration with buffer adjustments rather than with pH adjustments. The biological filter efficiency is compromised by descending pH, and pH = 6.75 is already well down on the curve. Now this is specifically in regard to a heavily stocked and copiously fed mixed community. It is not a Dutch garden or a blackwater biotope. Those are "expert systems" of a different kind and their defining criteria do not apply here; I am adhering to the conventional tenets of environmental engineering in the management of this habitat.

I use a filter bag containing aragonite and dolomite; crushed shells substrate, SeaChem Reef Reactor, and Brightwell NeoMag. At present there are about 750 grams of this in the filter stream. This accounts for a good deal of the calcium supplementation, and a little of the magnesium. As all of it is carbonate salts, a significant portion of the buffer derives from this as well. The rate of solute build is a function of the mass in the medium charge and the rate of flow through the charge. The water change regimen dilutes it at a specific rate. This is an effort to reconstitute, at least partially, both the GH and KH of the habitat, and it does do that. For a while I attempted to quantify the whole enterprise by adjusting the mass of the charge and the flow, but this proved to be impractical. It is far easier to get the right proportions by adjusting the dosed solutions of MgSO4, CaCl2, Ca(NO3)2, and K2CO3. The aragonite in the filter merely holds up the "floor" level.

In a planted tank the evolution of polyphenols is inevitable. Plant matter expires and decays. Humus originating from aquatic plants is mostly humic acid, fulvic acid, and hydrophilic acid. In natural settings percolation of water through leaf litter and fallen wood picks up tannic acid also. All these are polyphenolic acids and do affect the pH of the water. If present in significant concentration, they skew the pH/KH relation which will bias the CO2 calculation. I am aware of this fact and am certain that in this densely planted, biologically mature aquarium humus is being generated constantly. The humus is a part of the total DOM. I have no means of reliably measuring it, and assume that the water change regimen deals with it effectively, so I regard it as negligible.

The swordplants are putting out quite a lot of runners, including the E grisebachii 'Tropica', which is producing two, with plantlets. The lotus is shading the entire tank now. I have turned all the lights up to 100%.

Today's numbers

pH: 6.75
TDS: 300 ppm
ORP: 521 mV
NO3: 13 - 18 ppm
PO4: 0.98 ppm
K: 30 ppm
Fe: 0.06 ppm
dKH: 5.4 (97 ppm)
CO2: 26.3 ppm
dGH: 4.7 (84 ppm)
Ca: 18.4 ppm
Mg: 9.3 ppm
Ca/Mg: 2.0

Nitrate has two sources in this system at present. The sole allochthonous source is Ca(NO3)2; I have suspended KNO3 entirely. The balance is the total autochthonous mineralized product of environmental metabolism, whose ultimate origin is largely fish food. I feed generously. Much of what is put in is fresh-frozen. As I test frequently, I have tried to draw conclusions about whether feeding of the fish in a heavily stocked aquarium is alone a sufficient source of nitrogen for dense vegetation. With the SWCR operating, I have in the past caused a nitrogen limitation condition, with NO3 being near zero for days at a time. (Not a good outcome, and I'll leave it there.) My interpretation now is that the current dosing rate of Ca(NO3)2 is properly calibrated with the SWCR to define the range floor of NO3 concentration, while feeding levels, somewhat variable, move the concentration within the range and mitigate downward drift.

Calcium has two sources: the hardness reconstitution reactor filtrant, and the allochthonous supplementation. The latter is a 50/50 mix of Ca(NO3)2 and CaCl2 solutions. At the current dosing rate, Ca +2 is being well maintained. I should note here that the more commonly used compound for Ca +2 supplementation, CaSO4, is not used in my system because of its difficult solubility. It works okay dropping it into the water column, there being allowed to slowly dissolve in situ. But it is unsuitable for autodosing because it sedimentates in the vat and clogs the lines. Ca(NO3)2 is the perfect answer for this for its easy solubility and as a source of NO3.

Orthophosphate concentration is highly variable. Recently I stopped KH2PO4 dosing and the only source of phosphorus has been autochthonous product. The variability is related to the feeding schedule, but the latency is difficult to track and I have given up trying to quantify this relation with any certainty. I have set the upper limit for PO4 at 2.5 ppm. If downward drift persists I can resume dosing for a while.

The only source for potassium is K2CO3. This is easily soluble so is effective for autodosing buffer. The current rate of KH replenishment is also holding K +1 at 30 ppm, a "luxury uptake" concentration. With previous similar SWCR schedules the K +1 concentration held around 40 ppm. This was unnecessarily excessive, but reducing the dose knocked down the buffer. The reason for dosing K2CO3 in the first place is to maintain the KH at the scheduled SWCR. The aragonite medium in the hardness reconstitution reactor closes the gap a bit, but I am also mixing SeaChem Alkaline Buffer with the K2CO3. It doesn't take much to get the balance.

Today's numbers

TDS: 340 ppm
NO3: 13 - 18 ppm
PO4: 2.27 ppm
K: 20 ppm
Fe: 0.16 ppm
dKH: 5.6 (100 ppm)
CO2: 27.1 ppm
dGH: 4.1 (74 ppm)
Ca: 19.2 ppm
Mg: 6.3 ppm
Ca/Mg: 3.1

These parameters are about right, but I am tinkering a bit.

Graphs below are Redox, Oxygen, and pH profiles for the last 7 days. The small drop in yesterday's DO peak is due to reduced light (leaving the canopy lid up). Last Friday morning's pH spike shows suspension of CO2 injection during the filter change operation.

Closes and opens in a diurnal cycle. Also 2" taller!

Today's numbers

pH: 6.75
TDS: 330 ppm
PO4: 2.38 ppm
K: 30 ppm
dKH: 5.6
CO2: 27.1 ppm
dGH: 4.5
Ca: 19.2 ppm
Mg: 7.8 ppm
Ca/Mg: 2.5

I am not an expert in this plant, so I would be pleased to have comment.

This is Nymphaea rubra. It is a 'tropical' rather than a 'hardy', or 'temperate', waterlily. It is rhizomatous and propagates from tubers. The first blossom opening spreads the petals but reveals little of the central parts. The second opening reveals the outer ring of stamens. In the third opening, shown here, the stamens are spread wide and are loaded with pollen. If there is a pistil present I am not finding it. Is this species protogynous?

The life-style strategy of this waterlily endows it with the aerial advantage, the stoma being on the upper surface of its sizable, and numerous, leaves. The shoots are packed with canals that move gases and fluids between the leaves and the rhizomes. This must be generally beneficial to the health of the substrate. The hydrophobic "lotus effect" seems to be entirely lacking as water drops do not bead on the leaves. On tranquil water leaves float evenly and remain dry to their outer margins. Fully or partially submerged leaves where current overflows them tend to yellow and do not thrive.

As expected, there will be only three diurnal cycles for this flower. The plant is ceasing support.

I have examined the details of the stalks of the waterlily and made these sketches. The stalks are bundles of canals, of course, and it is clear that a prodigious quantity of materials are trafficked between the emergent organs and the rhizome. This plant fascinates me and I am interested in learning about its anatomy and physiology in greater detail. Anyone familiar with technical literature on waterlilies, please make some suggestions.

Flowering requires a lot of energy, and the stalk, being the infrastructure, is accordingly elegant. It is wondrous how a living thing can extract energy from its environment and fold that energy into its own being. All life does this, but the phenomenon is ubiquitous in our everyday experience on this planet, so we largely take it for granted. Consider the waterlily, how it grows.

This plant is dominant and I regard it as a keystone individual in the ecology of this habitat. There is a definite correlation between the production rate of the waterlily and that of algae, generally. Front glass build-up of common Chlorophyte is very obviously in inverse relation to number of floating leaves, and the suppression of various algae throughout the tank is evident as well. Probably much of this is due to shading, as the waterlily coverage is extensive. I believe other factors are in play too (another topic perhaps). For one, I believe other plants benefit from the rhizosphere the waterlily generates.