Garam Laut Akuarium & Air RO: Mixing Saltwater Correctly in Malaysia

Garam laut akuarium (aquarium marine salt) is a specially blended salt that recreates natural seawater, with sodium chloride plus magnesium, calcium, potassium, carbonates and trace elements. To make saltwater for a marine tank, mix it with RO (reverse osmosis) or RO/DI water, not tap water, until salinity reaches about SG 1.024–1.026 (roughly 33–35 ppt), then let it circulate before use. Top off evaporation with fresh RO water only, never more saltwater. This guide explains why, and gives a simple mixing routine for Malaysian homes.

Why Not Tap Water or Table Salt?

Option	Why it's a problem
Table salt (garam dapur)	Almost pure sodium chloride; lacks magnesium, calcium and buffers; may contain iodine or anti-caking additives
Freshwater aquarium salt (garam ikan)	Made for freshwater treatments, not for recreating seawater
Malaysian tap water (air paip)	Chlorinated (the national standard allows residual chlorine up to 5 mg/L); may carry phosphate, nitrate, silicate and metals that fuel algae and harm corals
Beach seawater	Inconsistent salinity, possible pollution and parasites, especially near towns and ports
Marine salt + RO water	Consistent, clean and predictable. The standard choice

Anti klorin removes chlorine, but it doesn't remove phosphate, nitrate or silicate. A fish-only tank can sometimes cope with dechlorinated tap water, but reef tanks with corals and invertebrates do much better on RO water. Read our Malaysian tap water guide for the freshwater side.

RO and RO/DI Water Basics

RO (reverse osmosis) forces water through a fine membrane that removes most dissolved solids. DI (deionisation) resin is an extra stage that polishes out what's left.

Stage	What it removes
Sediment filter	Dirt, rust, particles
Carbon block	Chlorine and chloramine (protects the membrane)
RO membrane	Most dissolved salts, metals, nitrate, phosphate
DI resin	Remaining traces, especially silicate

Malaysian options:

• Home RO/DI unit: the most convenient if you keep a reef. Check the TDS of the output with a TDS meter; RO/DI water should read close to 0.
• Bought RO water: some aquarium shops sell it, and refill stations sell purified water. Ask what treatment it has had, because not all "filtered" water is true RO.
• Waste water: RO units send some water to drain. Many hobbyists collect it for mopping or plants.

Garam Laut Akuarium: How to Mix Saltwater Step by Step

1. Use a clean, food-grade bucket or container reserved only for saltwater.
2. Fill with RO water to a marked level so you always know the volume.
3. Add a small pump or powerhead to circulate. A heater is rarely needed in Malaysia; room temperature is usually close to tank temperature.
4. Add salt gradually to the moving water. Check the salt brand's label for the dose per litre.
5. Let it mix for several hours, ideally overnight, until clear and fully dissolved.
6. Measure salinity (see below) and adjust: add salt to raise it, RO water to lower it.
7. Match temperature to the tank before a water change.

Never add dry salt directly into a tank with livestock in it.

Measuring Salinity

Tool	Accuracy	Notes
Swing-arm hydrometer	Rough	Cheap; air bubbles and wear affect readings
Refractometer	Good	The standard hobby tool; calibrate with RO water or calibration fluid
Digital salinity meter	Good	Convenient; needs calibration

Target salinity

Tank type	Specific gravity	Approx. ppt
Reef with corals	1.025–1.026	34–35
Fish-only / FOWLR	1.022–1.025	30–34

Stability matters more than hitting an exact number. Calibrate your refractometer regularly, and check salinity every week. Find refractometers and reef test kits under marine test kits.

Top-Off: Freshwater Only

When tank water evaporates, only the water leaves; the salt stays. So:

• Top off with RO water, not saltwater. Adding saltwater to replace evaporation will keep raising salinity.
• Use saltwater only for water changes, where you remove old saltwater and replace it with new.
• Malaysian heat and cooling fans speed up evaporation. An auto top-off (ATO) keeps the level, and salinity, steady. See our nano reef guide for why this matters in small tanks.

Common Mistakes

1. Topping off with saltwater, causing salinity to creep up.
2. Using a hydrometer without checking it against a calibrated refractometer.
3. Mixing salt in tap water and then fighting algae for months.
4. Using new saltwater immediately, before it's fully mixed.
5. Storing mixed saltwater uncovered for weeks; keep it covered and circulated, and use it reasonably soon.
6. Skipping parameter tests: check alkalinity (KH), calcium and magnesium once you keep corals.

How Much Salt and Water Will You Need?

Water changes of about 10–20% every 1–2 weeks are common. For a 2-kaki tank holding about 55 L, that's roughly 5–11 L of new saltwater per change, plus top-off water. Buy salt in a size that suits your routine, and store it sealed and dry. Malaysian humidity can make opened salt clump.

For the bigger picture of starting a saltwater tank, read akuarium air laut untuk pemula.

Frequently Asked Questions

Boleh guna garam biasa untuk akuarium air laut?

Tidak boleh. Garam dapur hanya mengandungi natrium klorida dan tiada magnesium, kalsium serta mineral lain yang diperlukan oleh ikan laut dan karang. Gunakan garam khusus untuk akuarium laut.

Air RO perlu ke untuk akuarium laut?

Untuk akuarium karang (reef), air RO sangat digalakkan kerana air paip mengandungi klorin, fosfat dan nitrat yang boleh menyebabkan lumut. Untuk tangki ikan sahaja, sesetengah orang guna air paip yang dirawat, tetapi hasilnya kurang stabil.

What salinity should a marine tank be?

For reef tanks, about SG 1.025–1.026 (34–35 ppt). Fish-only tanks are often kept slightly lower, around 1.022–1.025.

Why does my salinity keep rising?

Evaporation. Water leaves but salt stays. Top off daily with RO water, or use an auto top-off.

How long should I mix marine salt before use?

At least a few hours with a pump running, and ideally overnight, so the salt fully dissolves and the water stabilises.

---

Shop marine salt, refractometers and marine test kits from Malaysian sellers on FishyHub. Check each listing for pack size and delivery options.