2HR Aquarist APT SKY – Remineralizer for Aquascaping

2HR Aquarist APT SKY – Remineralizer for Aquascaping

APT SKY is a GH booster and remineralizer built specifically for RO/RODI water in planted aquariums. It raises general hardness (GH) by replenishing calcium and magnesium without touching NPK values, KH, or pH — a distinction that matters if you're running a carefully balanced fertilization routine and don't want your remineralizer interfering with it.

What Makes APT SKY Different

Most remineralizers on the market shift more than just GH — some nudge KH and pH along with it, which can complicate dosing for aquarists who need those parameters to stay put. APT SKY is formulated to raise GH in isolation, so it plays well alongside whatever fertilization and CO₂ setup you're already running.

It's also roughly three times more concentrated than standard remineralizers. Each 5 ml (or 3.5 g) added to 60 litres delivers 12 ppm calcium and 3.5 ppm magnesium, raising GH by about 2.5 dGH — a predictable, repeatable increment rather than guesswork.

Key Benefits

• Raises GH without altering KH, pH, or NPK levels
• Highly concentrated — a small dose covers a large volume
• Fast-dissolving, non-caking powder formula
• Safe for shrimp and demanding soft-water plant species
• Predictable dosing: 5 ml per 60 litres raises GH by roughly 2.5 dGH

Composition

• Calcium (Ca): 21.5%
• Magnesium (Mg): 5.4%
• Iron (Fe): 0.06%
• Trace elements: Boron, Copper, Manganese, Molybdenum, Zinc
• Seaweed extract: Less than 1%
• Form: Powder (fast-dissolving, non-caking)

Who Should Use APT SKY

• Anyone using reverse osmosis (RO/RODI) water — remineralization is essential before this water is aquarium-safe
• Soft water aquariums housing shrimp or demanding plant species
• Tanks mixing shrimp and hard-water plants alongside soft-water species
• Aquariums with GH below 5 dGH — the recommended target range is 5–8 dGH

If your fish or invertebrates also need a moderate KH buffer and stable pH — for example guppies, mollies, or snails — APT SKY PLUS is the better fit, since it raises KH to roughly 2 dKH and buffers pH to 7.2–7.6 alongside GH.

Dosing Instructions

• For RO/RODI water: 15 ml per 60 litres as a starting dose
• For soft tap water: test your current GH and use 2HR Aquarist's dosing calculator to fine-tune the amount
• During water changes, dose based on the volume of new water added, not the total tank volume

Expert Tip

Don't guess your GH — test it before your first dose, and again a day after dosing, especially if you're new to remineralizing RO water. Building up GH gradually over a couple of water changes is gentler on shrimp and fish than pushing straight to your target in one go, particularly if the tank has been running very soft for a while.

Frequently Asked Questions

Does APT SKY affect KH or pH?

No. APT SKY is formulated to raise GH only, without shifting KH, pH, or NPK levels.

Is APT SKY safe for shrimp?

Yes, it's specifically suited to soft water aquariums with shrimp and demanding plant species.

How much APT SKY should I use for RO water?

Start with 15 ml per 60 litres of RO/RODI water, then test and adjust based on your target GH.

What's the difference between APT SKY and APT SKY PLUS?

APT SKY raises GH only, leaving KH and pH unchanged — ideal for tetras, soft-water plants, and shrimp. APT SKY PLUS also raises KH moderately and buffers pH, better suited to livebearers and snails.

How do I dose APT SKY during regular water changes?

Base the dose on the volume of new water you're adding, not the total tank volume.

Pairs Well With

• APT 3 or APT 1 – for plant fertilization
• APT Start – when setting up a new aquarium with RO water