Red Sea Salts - 4 kg (120 Ltr Bag)
Cost per litre
$0.29
Water type
Marine + Reef
Red Sea Salts - 4 kg (120 Ltr Bag)
Our best cost-per-litre pack in the Red Sea Salt range. Red Sea Salt is a premium reef-grade marine salt mix that dissolves fast and clean to a balanced calcium, alkalinity and magnesium profile. This 4 kg bag mixes to roughly 104 L at full reef salinity — enough for a run of water changes on a small-to-mid system — and, litre for litre, it costs less than either the 2 kg bag or the 22 kg bucket we stock.
Key features
- One salt, three targets — the same formula mixes to a lighter fish-only salinity, a mid invertebrate salinity, or full reef salinity, just by changing how much you dose. See the mix ratio table below.
- Dissolves fast and clear — no cloudiness or residue once mixed and aerated.
- Free of nitrate and phosphate — won't feed algae or push a reef tank off balance.
Mix ratio and resulting parameters
| System type | Dose | Salinity | Calcium | Alkalinity | Magnesium |
|---|---|---|---|---|---|
| Fish-only | 33.4 g/L | 31.0 ppt | 365–395 mg/L | 6.8–7.3 dKH | 1,100–1,180 mg/L |
| Non-coral invertebrates | 36.0 g/L | 33.5 ppt | 390–420 mg/L | 7.3–7.8 dKH | 1,170–1,230 mg/L |
| Coral and reef | 38.2 g/L | 35.0–35.5 ppt | 415–445 mg/L | 7.7–8.2 dKH | 1,240–1,320 mg/L |
Add salt to water, not water to salt. Mix vigorously without aeration for 30 minutes to 2 hours until the pH settles at 8.2–8.5, then bring the mix to tank temperature and check salinity with a refractometer before use.
Which pack size is cheapest per litre?
| Pack | Litres at reef salinity |
|---|---|
| 2 kg bag | ~52 L |
| 4 kg bag | ~104 L |
| 22 kg bucket | ~575 L |
The 4 kg bag is the cheapest per litre of the three sizes we stock. If you're only topping up a nano tank the 2 kg bag still makes sense, and if you'd rather change bags less often the 22 kg bucket is more convenient — but on price per litre alone, this is the one to buy.
Suitable for, and not suitable for
Suitable for fish-only, invertebrate and coral/reef marine systems — the target salinity changes, the salt doesn't. Not a substitute for Coral Pro Salt if you're chasing higher baseline alkalinity for SPS-heavy growth; the two can be swapped between, but only gradually (max 15% of a water change at a time) because of the alkalinity step up.
Care and maintenance
Store the sealed bag somewhere dry — a damp storage area will clump the salt before you get to use it. Mix in a clean, dedicated bucket and let the water reach tank temperature before dosing, to avoid a temperature shock on the tank it's going into.
Warranty and delivery
Sold as a consumable, not a warranted item beyond your consumer guarantee rights under Australian Consumer Law — if a bag arrives damaged or short-filled, contact us for a replacement.
Common questions
Why is the 4 kg bag cheaper per litre than the 22 kg bucket?
It comes down to how each pack size is currently priced, not a difference in the salt itself — check the comparison table above rather than assuming the biggest pack is automatically the cheapest.
How much water does a 4 kg bag actually make?
Around 104 L mixed to full reef salinity (38.2 g/L). Mixed lighter, for a fish-only tank at 33.4 g/L, the same bag goes further — about 120 L.
What's the difference between this and Coral Pro Salt?
Coral Pro Salt carries a higher baseline alkalinity aimed at faster SPS coral growth. Elemental composition is otherwise similar, and you can switch between the two — just do it gradually across water changes rather than all at once.
Is this the same formula as the 2 kg and 22 kg packs?
Yes — identical salt, just a different pack size and price point.
