The Dutch 90P
Nineteen species of stem plant in a Dutch street scape, on fresh aquasoil, with CO₂ injected through an inline diffuser. Temperature, pH and conductivity are logged continuously and published straight from the tank; PAR is measured by hand at each plant. The figures below are the recorded values, not a summary of them.
Recorded Data
Every figure below is a count taken from the database at page load, not a number typed into the page. Each one links to where the underlying data can be seen.
Project Purpose
This is my 90P Dutch tank, the third layout in it and the first documented well enough that the next version can inherit more than photographs and memory. I document it with measurements rather than impressions. PAR, water chemistry, plant development, equipment changes and operating conditions are tracked over time to better understand what produces healthy growth and strong coloration. The reasoning behind that approach is set out in the measurement philosophy.
The goal is to create a useful, transparent record of the tank’s development and eventually publish a controlled comparison between the original ADA Solar RGB and the Solar RGB II.
Planted Species
Every species in the tank, with the PAR measured at that plant. Values update as new readings are logged.
Cycle Progress
Fresh ADA Amazonia leaches ammonia for the first few weeks, so a new scape is run on heavy water changes until it stops. Here is that curve, measured rather than assumed, and the tank growing in underneath it.
Hand-tested with a Seachem ammonia alert and a liquid kit. Once this sits at zero across consecutive tests, the water-change schedule can taper off the every-other-day startup cadence.
PAR Measurement Method
- Meter
- Apogee MQ-510 underwater quantum meter
- Measurement type
- Underwater PPFD measurements
- Fixture
- Chihiros WRGB II Pro 90, suspended, R86 G86 B95 W15
- Tank format
- 90P
- Measurement locations
- Nineteen live positions corresponding to plant groups, numbered against the original twenty
- Sensor position
- Held level at the measured plant or substrate location
- Conditions
- Aquarium light on, room lighting minimized, water clear
- Purpose
- Evaluate usable light distribution across the planted layout
PAR values represent the measured light at each recorded location. They are not universal plant requirements and should be interpreted alongside CO₂, nutrients, plant health, spectrum and canopy height.
PPFD by Plant Position
14 underwater measurements were recorded at the planted locations shown above. The table compares the measured PPFD at each position with a practical working range used to evaluate whether light may be limiting growth or coloration. A figure quoted for a fixture over open water does not say what the plant in the corner is getting. Measured mid-photoperiod with an Apogee MQ-510 held level at the plant, fixture 7.25″ above the water · September 18, 2026.
PPFD by Position, Ascending
| working range | ||||
|---|---|---|---|---|
| 09Pogostemon stellatus | 70 | 70–110 | 6″ | Within working range |
| 07Rotala 'Blood Red' | 80 | 90–150 | not recorded | Lower than working range-10 |
| 10Hygrophila 'Kompakt' | 80 | 40–70 | 6″ | Above working range+10 |
| 11Ludwigia arcuata | 80 | 60–100 | 6″ | Within working range |
| 13Staurogyne repens | 100 | 25–50 | 6″ | Above working range+50 |
| 14Micranthemum 'Monte Carlo' | 100 | 50–90 | 6″ | Above working range+10 |
| 18Ludwigia 'Pantanal' | 100 | 90–130 | not recorded | Within working range |
| 20Rotala macrandra 'Mini' | 100 | 90–130 | 6″ | Within working range |
| 03Alternanthera reineckii 'Mini' | 110 | 70–110 | 10″ | Within working range |
| 04Myriophyllum 'Guyana' | 115 | 40–70 | 10″ | Above working range+45 |
| 06Rotala 'Orange Juice' | 115 | 70–110 | not recorded | Above working range+5 |
| 02Lobelia cardinalis 'Mini' | 123 | 50–90 | 10″ | Above working range+33 |
| 15Alternanthera 'Super Magenta' | 125 | 70–110 | 6″ | Above working range+15 |
| 08Limnophila hippuridoides | 175 | 70–110 | 6″ | Above working range+65 |
Working ranges are practical targets for good color and form in this tank. They are not fixed biological thresholds. They are this project's own targets, not figures taken from a reference: the four most cited sources disagree about what a planted tank needs by up to five times, and the only per-plant table among them was produced with a lighting manufacturer. The survey sets them side by side. Light is one input among several: CO₂, nutrients, spectrum and canopy height all bear on color too.
Lighting
Current fixtureCurrent
Chihiros WRGB II Pro 90
- Hung over the tank on the 17th of September 2026, replacing the pendant
- Channels Red 86, Green 86, Blue 95, White 15
- Ramp begins 9:00am, full output 9:30am, ramp down 3:30pm, off 4:00pm
- PAR distribution measured here with an Apogee MQ-510; the manufacturer publishes none
Previous fixture, retainedCurrent
Original ADA Solar RGB
- Purchased from Aqua Forest Aquarium approximately six years ago
- No dimming, so it ran at its one output whenever it was on
- The standing PAR survey was taken under it and remains the comparison baseline
- Kept rather than sold until the comparison is finished
Planned comparisonPlanned
ADA Solar RGB II
The measured constraint on this tank is coverage rather than peak output. The lever for coverage is mounting height, and raising the current fixture made the ends worse because it has no output to spare. The second-generation fixture is stated to be about 1.5 times brighter, and that surplus is what would pay for hanging it higher. Whether it nets out better at the edges of a 90 cm tank is an open question: no PAR distribution figures for it appear to have been published anywhere.
The recorded prediction is that the extra output will buy enough height to leave the ends better off than they are today. It is on record so it can be shown to be wrong. The comparison uses the same aquarium, meter, measurement positions and procedure for both fixtures, at a matched height and again at each fixture’s own best height, and the result will be published whichever way it goes.
- Nineteen point PAR map
- Center to edge distribution
- Substrate and canopy measurements
- DLI comparison
- Fixture height comparison
- Photographs at matched settings
- Written findings and methodology
Experiments
Current Conditions
CO₂ goes in through an inline diffuser, held under pH control: a Raspberry Pi captures the degassed pH each morning and holds a target drop off that baseline through the photoperiod. This project uses pH drop as an operational control signal rather than an absolute dissolved CO₂ measurement. At near-zero KH the pH/KH table does not apply, so no ppm figure is published here.
Dissolved solids climb as the tank consumes and evaporates, then drop sharply at each water change. Every sawtooth in this trace is a ~53% change. Tracking the creep is what sets the change schedule, rather than a fixed calendar.
Water chemistry · hand-tested with liquid kits
- KH
- 0 dKH · 43d ago
- GH
- 6 dGH · 43d ago
- TDS
- 103 ppm · 88d ago
- Ammonia
- 0 ppm · 51d ago
RODI remineralized with a GH-only booster, so all hardness is deliberate. Near-zero KH is the intended state on fresh aquasoil, not a fault.
Hardware and Software
CO₂ automated on a schedule
CO₂ is injected on a fixed schedule with hardware safety limits. I have not closed the loop around pH because active aquasoil and near-zero KH complicate the relationship between pH and dissolved CO₂, while frequent on/off control can produce less stable injection. The logged pH curve is currently used to review and tune the schedule rather than switch the solenoid continuously.
Continuous sensing
Continuous sensor data is collected automatically; hand tests and PAR measurements are logged separately.
Light, quantified
PAR is logged per plant against a practical working range, so light distribution can be evaluated by position rather than inferred from one center reading.
Setup
Aquarium
- Format
- 90P · 90 × 45 × 45 cm rimless
- Estimated operating water volume
- Approximately 142 L (~37.5 US gal) after substrate, equipment displacement and headspace
Lighting
- Fixture
- Chihiros WRGB II Pro 90
- Shade
- ADA Shade fitted
- Mounting height
- 12″ (about 30 cm) above the water
- Output
- Fixed. No dimming
- Photoperiod
- 9:30am – 4:30pm
Filtration and flow
- Canister
- EHEIM Professionel 5e 700
- Second filter
- ADA Super Jet ES-600
- Surface skimmer
- ADA Vuppa II
- Flow
- Scheduled day / night profile
CO₂
- Control
- Fixed daily schedule with hardware safety limits; pH logged and used to tune the schedule
Substrate
- Base
- Power Sand
Fertilization
- Ferts
- 2Hr Aquarist APT
Water
- Source
- RODI · SpectraPure membrane + Pentek prefilters + SpectraPure DI
- Remineralized
- GH booster. Measured 0.0 dKH and 6 dGH on 8 August 2026
- Top-off
- Automatic (ATO)
Monitoring
- Controller
- Neptune Apex
- pH probe
- Milwaukee MA911B/2
- Conductivity
- Atlas Scientific EZO K0.1
- Automation
- Raspberry Pi running Pearl
Livestock
- Shrimp
- Amano shrimp, added 1 August 2026 once ammonia held at zero
- Fish
- Seven cardinal tetras, returned 8 August 2026 once nitrite also read zero
Product names match the live inventory that runs this tank. Linked items have a documentation page covering why they were chosen and what has been observed using them.
Measured and logged with Pearl, a self-hosted dashboard that monitors and runs this tank. Live figures updated Sep 21, 12:45 PM CT.