Red Sea 4-Part RCP Medium Pack — Complete Reef Care for a 300 L (80 gal) Reef

Red Sea's 4-Part RCP, also sold as Complete Reef Care, condenses a shelf of additives into four bottles. The 36 major, minor and trace elements a reef tank steadily uses up, alkalinity components included, are split across the four parts and pre-balanced in the ratio the reef consumes them. From there, a single weekly calcium test sets the dose for all four.

Red Sea walks through the program:

What is in each of the four bottles

• Part 1: calcium, magnesium, strontium and barium
• Part 2: the KH / alkalinity components
• Part 3: potassium, boron and the halogens iodine, bromine and fluorine
• Part 4: iron, manganese, cobalt, copper, aluminum, zinc, chrome, nickel, plus 18 other bioactive trace elements

One calcium test a week

The four parts are dosed on a fixed ratio. Red Sea's own example: if Part 1, the one carrying calcium, is 5 ml, Part 2 will be 10 ml and Parts 3 and 4 will be 2.5 ml each. You set the recommended starting doses, then adjust them as calcium uptake shifts over the months.

Run through a ReefDose 4, the whole program collapses into one setting: change the daily dose of Part 1 and the unit adjusts Parts 2, 3 and 4 on its own. The bottles are supplied in the same ratio they empty, so all four run out together.

Red Sea shows the setup step by step:

The Medium Pack at a glance

• Built for a 300 L (80 gal) mixed reef
• Part 1: 1 L · Part 2: 2 L · Part 3: 0.5 L · Part 4: 0.5 L
• Red Sea puts the supply at roughly three months
• The middle size: the Small Pack covers 150 L, the Large Pack 600 L

4-part or 7-part?

The 4-part program is designed for systems without a refugium. In a tank with no refugium, coral growth is the dominant process driving water chemistry and the 36 elements deplete in a relatively fixed ratio, which is precisely what makes calcium-based dosing work. If your system runs a macroalgae refugium, Red Sea points you to the 7-part program instead (Reef Foundation and Trace Colors), where each element group is adjusted on its own.

Red Sea compares the two programs here:

Our advice

"I recommend the 4-part if you want great results while still enjoying the hobby: it is simple and it works. The 7-part, to me, is really for the person who wants to test everything and control everything. Personally, that is not my cup of tea."

"With a refugium, though, the 4-part does not work: the four parts stop being used up at the same rate, so it is no longer the one-test-for-everything method."

— Stéphane, Aquarium ReefSolution

The Reef Care Program in full

The 4-part is one branch of Red Sea's wider Reef Care Program. The first video introduces the program, the second covers the research behind the fixed ratio.

Why buy it from ReefSolution

Aquarium ReefSolution is an authorized Red Sea dealer. We ship across Canada, and if you are torn between pack sizes or between the two programs, our Laval store will walk you through it.

• ReefDose 4: the four-head doser that treats the program as a single product, Part 1 driving the other three.
• Coral Pro Salt: the starting point of the program, balanced seawater before any supplementation.
• Reef Energy Plus AB+: coral nutrition, a separate job from mineral supplementation.

Independent review

An independent hobbyist walkthrough of the whole Red Sea Reef Care line, useful if you are deciding between programs. It is not produced by Red Sea or by our store.

Frequently asked questions

Can I dose on alkalinity instead of calcium?

Red Sea says no, and explains why: almost all the calcium is taken up by coral processes, while measured total alkalinity also includes borate, phosphate, fluoride, silicate, sulfate, nitrate and organic compounds, all affected by water changes, food and bacterial activity. Dosing all four parts off alkalinity builds up calcium and trace elements the corals never used.

I already run the 7-part program, can I move to the 4-part?

Yes, if your system has no refugium: Red Sea describes the move from 7-part to 4-part as a straight switch. With a refugium, stay on the 7-part.

How much do I dose to start?

Red Sea publishes an online tool, MyRecipe, that recommends starting doses for all four parts based on tank type, water volume and your goals. From there you adjust against your weekly calcium test.