Red Sea Salt 20kg Refill Box 600ltr
Cost per litre
$0.27
Water type
Marine + Reef
Red Sea Salt 20kg Refill Box 600ltr
One 20 kg refill box mixes 600 litres of stable, moderate-alkalinity reef seawater. Red Sea Salt is Red Sea's original marine salt mix, formulated to a natural, reef-stable alkalinity so it suits fish-only systems and reef tanks running on natural or lightly dosed nutrient levels. This refill box is the format for topping up a bucket you already own, rather than paying for a new bucket each time.
Key features
- Makes 600 litres — one 20 kg box mixed to reef salinity (35 ppt), roughly twelve 50 L water changes.
- Moderate, reef-stable alkalinity — 7.7–8.1 dKH at 35 ppt, closer to natural seawater than the elevated alkalinity of Coral Pro Salt.
- Dissolves fast and clean, with no cloudy residue left once fully circulated.
- Refill box format — less packaging than a bucket, and no empty bucket to store afterwards.
Specifications
| Pack weight | 20 kg |
|---|---|
| Makes | 600 L at reef salinity (35 ppt) |
| Alkalinity at 35 ppt | 7.7–8.1 dKH |
| Calcium at 35 ppt | 415–430 mg/L |
| Magnesium at 35 ppt | 1,230–1,290 mg/L |
| Potassium at 35 ppt | 375–395 mg/L |
| Format | Refill box — no bucket included |
Which pack size do I need?
We stock Red Sea Salt in three pack sizes. Cost per litre doesn't scale with pack size the way you'd expect, so it's worth checking the numbers rather than assuming bigger is cheaper:
| Pack | Makes |
|---|---|
| 10 kg bag | 300 L |
| 25.2 kg bag | 750 L |
| 20 kg refill box (this listing) | 600 L |
This refill box is priced for topping up a bucket you already own, not for the cheapest litre on the shelf — the 10 kg bag currently costs less per litre. If cost per litre matters most and you don't need the box format, it's worth comparing against the other two sizes first.
Dosage and directions
Mix into clean RO or RO/DI water with circulation until fully dissolved — allow around 20 minutes. Aerate before use, and match temperature and salinity to your display before adding. Use freshly mixed saltwater promptly rather than storing large volumes of made-up mix.
Suitable for, and not suitable for
Suited to fish-only systems and reef tanks running natural or lightly dosed nutrient levels, where a moderate, stable alkalinity is preferable to an elevated one. Reef tanks with heavy calcium and alkalinity demand from fast SPS growth are usually better matched to Red Sea's Coral Pro Salt, which mixes to a higher starting alkalinity and calcium level.
Care and maintenance
Store the unmixed salt sealed and dry — moisture reaching the box before mixing throws off the mix ratio. Once mixed, use within a few days rather than holding large volumes of made-up saltwater on hand.
Warranty and delivery
Sold subject to Red Sea's standard product guarantees, which apply in addition to your consumer guarantee rights under Australian Consumer Law. Ships as a standard parcel — no special freight handling required.
Common questions
Does the refill box come with a bucket?
No. It's designed to be decanted into a bucket or sealed container you already own, which is what keeps the cost per litre lower than buying a new bucket every time.
What's the difference between this and Red Sea Coral Pro Salt?
Red Sea Salt mixes to a moderate alkalinity, around 8 dKH, suited to fish-only tanks and naturally-run reefs. Coral Pro Salt mixes to a higher starting alkalinity and calcium level for reef tanks with heavier coral growth demand.
How far does 600 litres actually go?
It depends on your tank size and water-change routine — as a guide, that's around twelve 50 L water changes, or considerably more if you're only topping up a smaller system.
Is this the cheapest way to buy Red Sea Salt per litre?
Not necessarily — compare the current cost per litre for each pack size on the product page before deciding. Choose the refill box if you already have a bucket to decant into; choose the 10 kg bag if cost per litre is the deciding factor.
