• Sized for reefs to 300 L — built around roughly three months of daily dosing for a mixed reef at that volume.
• Four parts, one ratio — Part 1 (Calcium & Magnesium+), Part 2 (Alkalinity/KH & pH stabiliser), Part 3 (Iodine & Potassium) and Part 4 (Iron & Bioactive Elements), bottled so all four run out together.
• 36 major, minor and trace elements in the ratio found in coral skeleton and tissue.
• Manual or automated dosing — works by hand or through a Red Sea ReefDose.
• Set your dose from testing, using a Red Sea Reef Foundation test kit, rather than the label rate alone.

All three RCP packs dose the same four elements in the same ratio — they differ only in reef volume and cost per 100 L over the roughly three-month cycle.

For a 300 L reef dosed at the mixed-reef guide rate (~3 mL per 100 L per day), that's about 9 mL of each part daily — the Medium pack is sized so all four bottles last roughly three months at that rate.

Foundation elements (Parts 1 and 2) are formulated so 1 mL per 100 L raises calcium by 2 ppm, magnesium by roughly 1 ppm, and alkalinity by about 0.034 dKH — but the right daily dose is whatever your reef is actually consuming, not the label maximum.

Never exceed a daily increase of 20 ppm calcium, 0.5 meq/L (1.4 dKH) alkalinity or 10 ppm magnesium — spread any larger correction over several days. When dosing manually, add magnesium first, then alkalinity, then calcium, with about 10 minutes between each. Part 4 (Iron & Bioactive Elements) has no single target ppm — Red Sea's guidance is to dose it in proportion to how much of Parts 1–3 your reef is using.

Included: four dosing solutions — Calcium & Magnesium+, Alkalinity/KH & pH Stabiliser, Iodine & Potassium, and Iron & Bioactive Elements — proportioned for a 300 L reef over roughly three months.

Not included: dosing pump, test kits, and the calcium/alkalinity/magnesium test results you'll need to set your own daily dose accurately. A Red Sea Reef Foundation test kit and either manual dosing or a ReefDose unit are what you'll still need to run the programme properly.

Suitable for an established 150–300 L saltwater reef running coral, where calcium, alkalinity and magnesium need topping up against consumption.

Not suitable for fish-only or newly cycled tanks with no coral demand — dosing without a measurable uptake risks pushing parameters too high. Not a substitute for water changes, and not intended for freshwater systems.

Covered by the standard manufacturer guarantee against faulty product, in addition to your rights under Australian Consumer Law. Liquid reef additives ship as standard parcel freight from Brisbane; no special handling required for this pack size.

Do I need a test kit to use this?

You can dose to the tank-type guide above as a starting point, but Red Sea's own instructions recommend testing calcium, alkalinity and magnesium regularly and adjusting the dose to what your reef is actually using — dosing blind risks over- or under-shooting.

What's the difference between the Small, Medium and Large packs?

The same four elements in the same ratio — only the bottle sizes and the reef volume they're built for change. See the size comparison table above.

Can I dose all four parts at once?

Red Sea recommends spacing magnesium, alkalinity and calcium about 10 minutes apart when dosing manually, to avoid a local spike that can precipitate elements out of solution. The trace element part (Part 4) isn't time-sensitive in the same way.

Could I use the Large pack instead, to save on reorders?

Yes — the Large pack (up to 600 L) works fine on a 300 L reef; you'd just be dosing roughly half the bottle per day, so it lasts closer to six months instead of three, at a lower cost per 100 L. It's a larger upfront cost for the same total elements.

What happens if I miss a few days of dosing?

Corals will draw down calcium, alkalinity and magnesium from the water in the meantime. Test before resuming and dose to the measured deficit rather than doubling up the next day's dose, which risks a large swing.