API Leaf Zone

• Chelated iron and potassium – the two nutrients most likely to run short in a planted freshwater tank, in a form leaves can take up directly.
• Weekly dosing – 5 mL per 10 US gallons (37.9 L), measured with the bottle's dosing cap.
• Rated safe with fish and freshwater invertebrates – API states it's safe to use with all freshwater invertebrates, including shrimp and snails.
• Around 1c per litre of tank water dosed on the 237 mL and 473 mL bottles, and under 1c per litre on the 3.8 L – see the pack comparison below.
• Three pack sizes – 237 mL, 473 mL and a 3.8 L refill for larger planted setups or multiple tanks.

API's label rate is 5 mL for every 10 US gallons (37.9 L), applied once a week using the bottle's built-in dosing cap. Overdosing feeds algae as readily as it feeds plants, so measure rather than estimate.

Cost per litre of tank water dosed, calculated from the current price and API's label dose rate:

All three sizes work out to roughly a cent or less per litre dosed at the current price – the 3.8 L is the cheapest per litre if you're dosing several tanks and won't let the bottle go stale before you use it.

Suitable for:

• Freshwater planted aquariums, especially fast-growing stem plants
• Tanks that also hold fish and freshwater invertebrates such as shrimp and snails

Not suitable for:

• Marine or reef aquariums – this is a freshwater-only product
• Tanks already struggling with an algae bloom – API's own label notes the fertiliser stimulates algae growth, so it's the wrong product to reach for until the bloom is under control
• A substitute for root fertilisation – heavy root feeders such as swords and crypts still need a substrate fertiliser or root tabs

API's packaging and product page state the active nutrients as chelated iron and potassium. API does not publish an exact percentage breakdown for either nutrient on its consumer-facing product page, so no guaranteed-analysis figures are shown here – checked 7 August 2026.

• Keep out of reach of children.
• Dose with the bottle's measuring cap rather than by eye.
• Increase the dose gradually if you're not already running a fertiliser, and watch for algae response over the first few weeks.

• Seachem Prime – for conditioning the water changes that go alongside a fertilising routine.
• API Freshwater Master Multi Test Kit 5 in 1 – keep an eye on nitrate and pH while you're dosing a fertiliser.
• Marina Floating Glass Thermometer – plant growth tracks temperature as much as it tracks nutrients.

This is a consumable, so no manufacturer warranty period applies. That does not affect your rights under the Australian Consumer Law: if the product is faulty, unsafe or not as described, you are entitled to a remedy.

All three pack sizes ship as standard freight.

Will Leaf Zone cause an algae bloom?

It can if overdosed. API's own label states the product stimulates algae growth, and recommends dosing lightly and only as directed rather than assuming more is better.

Is Leaf Zone safe with shrimp?

Yes. API states Leaf Zone is safe to use with all freshwater invertebrates, including shrimp and snails, at the labelled dose.

Can I use Leaf Zone in a marine tank?

No. Leaf Zone is formulated and labelled for freshwater aquariums with freshwater plants only.

Do I need a root fertiliser as well?

If you're growing root feeders such as swords or crypts, yes – Leaf Zone feeds through the leaf, not the substrate, so heavy root feeders still benefit from a separate root tab or substrate fertiliser.

How much does a 473 mL bottle actually cost to run?

At the current price and API's label dose, the 473 mL bottle works out to around 1c per litre of tank water dosed, treating roughly 3,580 litres across the life of the bottle at one dose a week.