Nano Reef Dosing Schedule Two Part: Small Tank Alk Ca Mg

Two-part dosing is the cleanest way to keep a nano reef stable once coral demand exceeds what water changes can replace — typically around the three-month mark in a tank with growing LPS or early SPS. This nano reef dosing schedule two part guide lays out practical starting doses, test frequencies, and drift patterns specific to small volumes under 75 litres, where dosing errors compound fast. The figures come from logs across dozens of nano tanks we advise through Gensou Aquascaping at 5 Everton Park, including our own 45 litre AIO display system.

Quick Facts

• Two-part components: Part A (calcium chloride), Part B (sodium bicarbonate/carbonate)
• Typical starting dose: 1 ml per 40 litres daily of each part
• Magnesium dosed separately, weekly or biweekly
• Target parameters: Alk 8-9 dKH, Ca 420-440 ppm, Mg 1350-1450 ppm
• Test frequency: alkalinity 2-3x/week, calcium weekly, magnesium biweekly
• Start low, observe 7 days, adjust in 10-20% increments
• Never dose A and B within 30 minutes of each other

Why Two-Part Matters in Nano Volumes

In a 150 litre tank, a missed alkalinity dose shifts 1 litre of doser output against 150 litres of buffer — a small percentage swing. In a 40 litre tank, the same volume shift represents four times the percentage change. Nano reefs punish dosing errors that a larger tank absorbs. Two-part is the manually-dosable method of choice because it lets you observe consumption and dial in precisely, whereas calcium reactors and kalkwasser present their own nano-specific challenges.

Popular two-part brands in Singapore: Red Sea Foundation A/B/C, Brightwell Reef Code A and B, ESV B-Ionic, and homemade recipes following the Randy Holmes-Farley formulas. All work at the nano scale provided the solution is mixed accurately.

Calculating Your Starting Dose

Measure alkalinity on three consecutive mornings before dosing anything. The daily drop in dKH is your consumption rate. Typical drops by stocking level:

• Softies only: 0.1-0.3 dKH/day
• LPS dominant: 0.3-0.6 dKH/day
• Mixed reef with growing SPS: 0.6-1.2 dKH/day
• SPS dominant, mature: 1.0-2.0 dKH/day

For Red Sea Foundation B at standard dilution, 1 ml in 40 litres raises alkalinity by roughly 0.14 dKH. A nano tank losing 0.4 dKH daily therefore needs around 3 ml of B and 3 ml of A daily to hold steady.

A Practical Starting Schedule

Morning (08:00): dose Part B (alkalinity). Wait at least 30 minutes. Mid-morning (08:45): dose Part A (calcium). Split both doses into two or three smaller shots across the day if the total daily dose exceeds 5 ml per part — smaller shots prevent parameter spikes in a small volume. Use graduated syringes for accuracy; pipettes miscalibrate quickly with viscous Part A solutions.

Never add A and B simultaneously or in rapid succession. The two precipitate out as calcium carbonate if they meet at concentration, clouding the water and undoing the dose.

Testing Frequency and Which Kits

Alkalinity drifts fastest, so test 2-3 times a week minimum. Calcium drifts slower — weekly is sufficient. Magnesium drifts slowest — biweekly testing catches drift in time. Recommended kits in Singapore:

• Alkalinity: Red Sea Pro or Hanna Checker HI-755 ($60-110)
• Calcium: Salifert or Hanna HI-758 ($35-95)
• Magnesium: Salifert or Red Sea Pro ($35-50)

Log every test in a notebook or an app. Trends matter more than single readings. A drift from 8.4 to 8.0 over a week, even though both are “in range”, signals a dose increase before corals stress.

Magnesium: The Quiet Parameter

Magnesium consumes 0.1x to 0.3x the calcium uptake rate in most nano reefs. Red Sea Magnesium or a simple epsom-salts-plus-magnesium-chloride homemade blend both work. Dose 5-10 ml weekly for a 40 litre tank starting, and adjust against testing. Magnesium below 1250 ppm causes alkalinity and calcium to crash together as precipitation accelerates — a common nano tank disaster that looks like random parameter collapse but is actually magnesium depletion upstream.

Automation at Nano Scale

Manual dosing is fine for the first few months while learning the tank. Once consumption stabilises, a small dosing pump (Jebao DP-3, Kamoer X1 Pro, or the built-in doser on newer AIOs) saves morning time and improves stability. Calibrate each channel with a measuring cylinder over a full minute of running — pumps drift 3-8% from rated output. Program doses in three to six shots per day rather than one large shot.

When to Adjust the Schedule

If alkalinity climbs 0.3 dKH above target: drop both A and B by 15%. If it drops 0.3 dKH below: increase by 15%. Always change A and B together by the same percentage — imbalancing them shifts the Ca:Alk ratio which stresses corals. Hold changes for 7 days before the next adjustment. Hunting — making daily adjustments — destabilises the tank faster than patience.

Common Nano Reef Dosing Mistakes

Chasing calcium upward is the single most common error. Calcium between 400-450 ppm is fine; raising it to 500 does nothing for coral growth and accelerates precipitation. Second common error: dosing against a cheap, poorly-calibrated test kit. Pay for quality on alkalinity testing first — if the number is wrong, every dose is wrong. Third: assuming a two-week hiatus will not matter. Skipping a few days in a mature SPS nano crashes alkalinity by 4-6 dKH, and the bleaching shows up before you realise.

Temperature and Water Change Interplay

In Singapore ambient with a chiller, tanks held at 25-26 °C consume slightly less calcium and alkalinity than tanks at 27-28 °C. Chiller-maintained nano reefs may need 10-15% lower doses than identical stocking on fan-only cooling. A 15-20% weekly water change with a reputable salt mix (Red Sea Coral Pro, Tropic Marin Pro, Fritz RPM) replaces some alkalinity and calcium, which means your two-part schedule and your water change schedule should be calibrated together, not independently.

Related Reading

• Two Part Dosing Guide Reef Tank
• Best Two Part Dosing Marine Calcium
• Calcium Alkalinity Stability Reef
• Balling Method Reef Dosing Guide
• Reef Dosing Schedule Guide